A hostile shooter alert was issued at 6 p.m. on Feb. 18 at the University of Massachusetts Amherst, placing the campus under lockdown.

Daniel Fitzgibbons, UMass Amherst’s spokesman, said the alert was issued after a student reported seeing a man with a gun.

Witnesses reported two men–one armed with a handgun–assaulting a student on campus at 5:15 p.m.

Students across the UMass Amherst campus were urged to stay inside until the situation had been determined safe.

Minutes after the assault, a second shooter alert was issued, adding the possibility that a second shooter may have been involved. The campus issued an “all clear,” at 7:15 p.m., two hours after the lockdown order.

There were no reports of shots fired but the assaulted student suffered a minor laceration to the head and was hospitalized at Cooley Dickinson Hospital in Northampton, MA.

According to UMass Amherst campus police, the two suspects fled from the scene in a vehicle. Leads on the vehicle’s make or model are dim.

The incident occurred in Pierpoint Hall, southwest of the campus’ residential area.

“This was not a random act,” said UMass Amherst Police Chief Tyrone Parham. Reports say the victim was most likely targeted.

Events unfolded the next day on Feb. 19 when UMass Amherst police issued an arrest for 19-year-old William McKeon of Framingham. The teen surrendered to Framingham Police at the time and was held without bail until Feb. 22. McKeon was charged with armed robbery and assault and battery with a dangerous weapon.

McKeown’s charges were amended due to investigation findings that the gun in question was a BB gun. The charge is the same–assault and battery with a dangerous weapon–but the wording is changed to “BB gun.”

McKeon, who is not UMass AMherst student, pleaded not guilty and was later released after a $7,500 bail. He is under house arrest.