Four juveniles triggered a police response on the Princeton University campus this morning after they were seen with a green toy handgun that had been left with items discarded by students, according to police.

   Police later found the four juveniles near the University Place Wawa convenience store, near where the discarded gun was found, according to Princeton Borough Lt. David Dudeck.

   Lt. Dudeck said the juveniles face no charges in connection with the weapon, which turned out to be a green plastic handgun picked up near Dod Hall on campus.

   Police, however, are charging the juveniles with underage alcohol possession and marijuana possession after they were found with the drug and containers of alcohol during questioning.

   Police said the juveniles, who are not university students, likely picked up the alcohol near at one of the university’s discard tents, which are set up at the end of the academic year to house items left behind by students leaving for the summer.

   Lt. Dudeck said the woman who initially called police, who was 20 yards away and did not see that the weapon was actually a toy, acted appropriately.

   “It was the right thing to do,” said Lt. Dudeck. “The common sense thing to do is call the police.”

   University officials initially reported there was a male gunman on campus at around 10:30 a.m. and instructed all students and personnel to remain inside.

   Later public safety personnel locked exterior doors on many campus buildings.

   At least three helicopters were seen circling the campus as late as 12 noon, around the time the university issued an all-clear.