(CNN) -- Carrying an alligator bag on an airline flight is fine, but live alligators are banned from boarding. That might explain why a toothy reptile was slithering around Chicago's O'Hare International Airport on Friday.
Security guard Tineka Walker was on patrol at Terminal 3 when a passenger alerted her to the suspicious object under an escalator.
"I looked, I said, 'What?'" Walker told CNN affiliate WBBM-TV.
When Walker radioed for help, Chicago Police Officer Anthony Oliver thought at first it was a crock. "Figured somebody was messing with us," Oliver told WBBM.
No need to call Tarzan to wrestle the gator, which was only about 18 inches long. An airport worker used a broom and dustpan to capture it. Animal control picked it up from police and handed it over to the Chicago Herpetological Society.
"What if a little kid grabbed this, thinking it was a toy? That could do a nasty job," said Bob Bavirsha, a reptile rescuer with the group.
A major clue to how it ended up at the airport emerged on Twitter on Friday when someone posted photos of a man holding what appeared to be the same alligator.
"The patterns on an alligator are as unique as your fingerprints," Bavirsha said. "We can actually match this band right here with that band right there."
The man holding the alligator in the tweeted photos also had unusual markings -- a tattoo on his arm that could help investigators identify him.
The Twitter posting said the man was riding the Blue Line train, which goes to O'Hare.
"They probably realized they couldn't take it through checkpoint, and just let him go, but, oh my God!" Walker said.
The alligator will eventually find a new life in a reptile park -- after getting a few months of treatment for stunted growth, apparently from not being properly fed.