(CNN) -- Five University of Calgary students were stabbed to death Tuesday morning in what the city's police chief called "the worst mass murder in Calgary's history."
Chief Rick Hanson said about 30 students were at a house party celebrating the end of the school year Monday night when police received a call at 1:20 a.m. Tuesday for a stabbing.
Arriving officers discovered three men dead. A woman and another man who were found injured with stab wounds later died at the hospital, according to Hanson. "The scene was horrific" he said.
Matthew de Grood, a fellow university student, was charged with five counts of first-degree murder Tuesday afternoon.
Hanson said de Grood "obtained a large knife" at the house and began attacking his victims shortly after he arrived. "He targeted the victims one by one, stabbing them several times" said Hanson.
There was no known altercation between de Grood -- who was an invited guest -- and any of his victims leading up to the attack, Hanson said. He does not know why they were targeted.
The victims, who have not been named, ranged in age from 22 to 27. "These were all good kids" said Hanson. "They did nothing wrong."
De Grood, 22, is the son of a longtime Calgary police officer.
"(The suspect's parents) are absolutely devastated" said Hanson. "They feel so much pain for the families impacted by their son. They are heartbroken."
Hanson said the suspect had had no previous run-ins with police.
"This is a very shocking and tragic day for our students and our entire university family," said university President Elizabeth Cannon. "Our thoughts and condolences go out to the families of those who have lost their loved ones in this unimaginable and senseless tragedy."
A Calgary police statement says the identities of the victims will be released pending the completion of the autopsies, which is expected Wednesday.