One of two suspects in the Boston Marathon bombing is dead and a massive manhunt is continuing for another, authorities said early Friday.
In a long night of violence the two suspects killed an MIT police officer, injured a transit officer in a firefight, and threw explosive devices at police during their getaway attempt, authorities said.
Boston was in lockdown Friday as the search for the suspect continued. Boston Police Commissioner Edward Davis says the suspect at large is the one seen in the white hat in images of the Boston Marathon suspects released by the FBI Thursday. Davis says he is "armed and dangerous."
Federal sources have told CBS News national security correspondent Bob Orr that officials believe the suspect who is still alive is either wearing an explosive vest, or has explosives with him.
This afternoon, Connecticut State Police issued an alert that the suspect may be in a 1999 green Honda Civic with Massachusetts plates 116 GC7.
Furious manhunt: 1 officer, suspect killed
From Watertown to Cambridge, police surrounded various buildings as they searched for Suspect No. 2. Around 8:30 a.m., officers sprinted toward a house in Watertown, and reporters were pushed back more than a block as helicopters buzzed overhead. SWAT teams, FBI agents and armored vehicles assembled at the scene as sharpshooters across the street trained their guns at the house. They left the house around 9:30 a.m., and a few dozen Boston police officers with assault rifles and helmets then filed into the backyard of a red brick building down the street.
A few dozen Boston police officers with assault rifles and helmets then left that house and were filing into the backyard of a red brick building down the street that they raided at around 7 a.m.
"We believe this man to be a terrorist," said Davis.
Police evacuated residents in Cambridge who lived on the same block as the suspects, going door-to-door telling people to leave. Police told CBS News it is just a precaution, but they have roped off the area and residents were seen coming out with suitcases.
At one suspect's apartment building, on Norfolk Street in Cambridge, a CBS News producer at the scene witnessed a woman being taken away authorities, being dragged by her arms. It was not known if she was being arrested or resisting being evacuated.
Some time after police evacuated everyone from the premises, police yelled "Fire in the hole," and detonated something.
At a press briefing early Friday afternoon Col. Timothy Albenof the Massachusetts State Police said investigators are progressing in their search, having completed 60 to 70 percent of the Watertown area they wanted to cover. "There has been no apprehension at this point," he said.
Alben also announced there would be a controlled explosion later today in Watertown, at a house that was secured by police but deemed unsafe for investigators to search.
The Middlesex district attorney said the two men are suspected of killing a Massachusetts Institute of Technology police officer on campus late Thursday, then stealing a car at gunpoint and later releasing its driver unharmed. Hours earlier, police had released photos of the marathon bombing suspects and asked for the public's help finding them.
Authorities say the suspects threw explosives from the car as police followed it into Watertown. The suspects and police exchanged gunfire, and one of the suspects was critically injured and later died while the other escaped.
Boston in lockdown
Residents throughout the Boston area -- including Watertown, Cambridge, Waltham, Newton and Belmont -- have been advised to keep their doors locked and not let anyone in. The Boston Police Department warned residents to "stay home." Vehicles were barred from entering or leaving Watertown.
Public and private schools and universities throughout Boston are closed.
The University of Massachusetts Dartmouth ordered an evacuation of its campus, in response to information that a person being sought in connection with the Boston Marathon bombing is a registered student.
Public transit service in Boston has been suspended. Taxis were suspended in the morning, but were resumed in the afternoon. Amtrak service was also suspended indefinitely between Boston and New York. Peter Pan Bus Lines has suspended service to Boston, and Megabus has canceled buses between Boston and other cities.
The FAA has also imposed temporary flight restrictions in the Boston area. Logan International Airport is open but is operating under heightened security. JetBlue is allowing anybody scheduled to fly to or from Boston to change their ticket for free.
Officials for the Boston Red Sox (scheduled to play the Kansas City Royals at Fenway Park) and Boston Bruins (who were to play the Pittsburgh Penguins this evening) are awaiting a decision on whether tonight's games will be played.
"We're just following the lead of the city officials and we have no word yet on what's going to happen," Red Sox chief operating officer Sam Kennedy said, "but employees have been told to stay home. . . . we're just awaiting any word like everybody else."
While Boston is in lockdown, Connecticut State Police issued a statement saying they were investigating information that the suspect may be in a gray Honda CRV with Massachusetts plates 316 ES9. Connecticut State Police later told CBS News that the car -- registered to the suspect's brother -- was located in Cambridge.
Suspects of Chechnyan origin
The suspects were identified by law enforcement officials and family members as ethnic Chechen brothers from Dagestan, which neighbors Chechnya in southern Russia. They lived near Boston, and had been in the U.S. for about a decade after receiving asylum, an uncle said.
The two have been identified as Dzhokhar A. Tsarnaev, 19, of Cambridge, Mass., and his brother, Tamerlan Tsarnaev, 26. They are legal permanent residents of the U.S.
CBS News confirmed that Dzhokhar is an American citizen, having been naturalized on September 11, 2012.
Bob Orr reports that, according to federal sources, the family has had "brief contacts" with law enforcement over the years -- though not big enough for the family to be on the radar screens of law enforcement officials.
A law enforcement source told CBS News that Tamerlan Tsarnaev was arrested on a domestic violence charge in Boston in 2009. The source also said that Tamerlan had three Jihadi videos on his Internet accounts.
Tamerlan -- the suspect seen in FBI photos released Thursday as wearing the black hat -- was wounded in an exchange of gunfire with police during last night's pursuit. He was captured and rushed to Beth Israel Deaconess Medical Center in Boston, where he died at 1:35 a.m. Doctors said he had gunshot wounds and a blast injury. The wounds were throughout the trunk of the man's body, CBS Station WBZ reported.
Ruslan Tsarni, an uncle of the suspects, told CBS Station WBZ "it absolutely devastated me," upon learning that his nephews had been named a suspect in the Marathon bombing. "It's not comprehendable, in our family."
Tsarni told WBZ that his nephews had immigrated to the United States around 2000 or 2001, and have lived in Cambridge since that time.
According to Tsarni, Dzhokhar completed high school in Cambridge. Tsarni, who says he hasn't been in touch with the brothers since around 2009, told the station he believes that the brothers' parents may have moved back to Russia.
Informed of the unfolding situation that left Tamerlan Tsarnaev dead in a shootout, Tsarni said, "He deserved his. He absolutely deserved his. . . . They do not deserve to live on this earth."
Alvi Tsarni, another uncle of the suspects, told CBS News said he was shocked about learning news of his nephews. "It's not possible. My nephews can't do this stuff, there's no way," he said.
Tsarni said that after not having heard from his nephews for the past two of three years owing to "family problems," he received a call from Tamerlan Tsarnaev last night at 7 p.m. "Yesterday he called me, said, 'Forgive me,' just like this," Tsarni said.
He also said that Tamerlan's wife is an American, a Christian who had recently converted to Islam.
Meanwhile, the father of the suspects claims that his son who is still on the loose is a smart and accomplished young man, describing him as a "true angel."
Anzor Tsarnaev spoke with The Associated Press by telephone from the Russian city of Makhachkala on Friday after police said his sons Tamerlan had been killed in a shootout with the police and the other, Dzhokhar, was being pursued.
"My son is a true angel," the elder Tsarnaev said, claiming his son was a medical student in the U.S. "He is such an intelligent boy. We expected him to come on holidays here."
President Obama was briefed on the situation overnight, according to a White House official.
The MIT shooting on the Cambridge campus Thursday night was followed by gunfire and explosions in Watertown, about 10 miles west of Boston.
CBS News senior correspondent John Miller reports that the evening's events began with the robbery by the two suspects of a 7-Eleven convenience store in Cambridge, when they saw an MIT police cruiser searching the area.
"What we are now told is that it starts with the robbery of the 7-Eleven," Miller said. "That they encounter an MIT Police Officer, and rather than see, 'Is he going to follow us? Is he going to chase us?' it appears that they came up and engaged him, killed him in his police vehicle, took off."
The MIT officer who had been responding to report of a disturbance Thursday night was ambushed and shot multiple times, according to a statement from the Middlesex district attorney's office and Cambridge police.
The officer, who was later pronounced dead at Massachusetts General Hospital, was identified as 26-year-old Sean Collier.
The Middlesex district attorney's office said Collier was a Somerville resident who had worked at MIT since January 2012. Before that, he was a civilian employee of the Somerville Police Department.
Authorities said after the shooting, the two men rode off in a stolen police vehicle, then carjacked a man in a Mercedes-Benz, keeping him with them in the car for half an hour before releasing him at a gas station in Cambridge. The man was not injured.
The search for the vehicle led to a chase that ended in Watertown, where authorities said the suspects threw explosive devices from the car and exchanged gunfire with police at about 1 a.m. Friday. Dozens of police officers and FBI agents were in the neighborhood and a helicopter circled overhead.
A transit police officer was seriously injured during the chase, authorities said.
State police spokesman David Procopio said, "The incident in Watertown did involve what we believe to be explosive devices possibly, potentially, being used against the police officers."
During the gunfight, according to sources, Tamerlan Tsarnaev threw a bomb toward police who advanced on him. Tsarnaev was shot down.
His brother, Dzhokhar, then got back into the car to escape, backing over his brother's body in the process.
Five blocks away, Dzhokhar hopped out of the car and fled on foot.
Officer Richard Donohue, Jr., 33, was rushed to Mount Auburn Hospital in Cambridge, where he is in critical condition, reports WBZ.
Boston cab driver Imran Saif said he was standing on a street corner at a police barricade across from a diner when he heard an explosion.
"I heard a loud boom and then a rapid succession of pop, pop, pop," he said. "It sounded like automatic weapons. And then I heard the second explosion."
He said he could smell something burning and advanced to check it out but area residents at their windows yelled at him, "Hey, it's gunfire! Don't go that way!"
MIT said right after the 10:30 p.m. shooting that police were sweeping the campus in Cambridge and urged people to remain indoors. They urged people urged to stay away from the Stata Building, a mixed-use building with faculty offices, classrooms and a common area.
Hours later, MIT, which has about 11,000 students, said the campus was clear but the shooter was still on the loose.