A Butler man is facing aggravated assault charges after he allegedly stabbed a juvenile male in the back Friday night.

City police said Joseph R. Parker, 24, stabbed the boy on the stairwell of an apartment complex on the 400-block of West New Castle Street following a fight in the building’s courtyard about 10 p.m.

The boy was taken to Butler Memorial Hospital and then flown by medical helicopter to Allegheny General Hospital.

His condition was not known Saturday morning.

The teen’s name and age were not in the police report.

Police said the incident began as a fight among several men in the courtyard. Parker was dressed in military clothing and field gear.

During the fight, Parker threatened to pull out a grenade, police said. It was later discovered that he did not have a grenade.

However, Parker did have a large straight-blade knife. He threatened to cut the throat of another juvenile male in the courtyard, police said.

The fight continued to the stairs of the building, where Parker allegedly stabbed the boy.

Parker is charged with two counts of aggravated assault, possession of a prohibited offensive weapon, and terroristic threats. He is in the Butler County Prison where he is waiting to be arraigned by an on-call district judge.

Police are investigating the case.