Police said they are speaking with a second suspect.
“We are actively seeking him, and we’ve alerted authorities in his community of our warrant so we are hoping to have him in custody as soon as possible”, Parham said.
There were not reports of shots fired.
On Thursday evening, the university issued its first alert about an armed person on campus.
The UMass Amherst campus officials had asked students to shelter in place after reports of a hostile armed person at Pierpont Hall.
All residence halls at UMass Amherst are locked and have 24-hour swipe card security systems, but McKeown and his accomplice were “provided access to Pierpont Hall willingly by a UMass student”, police said. The two suspects fled campus after the incident.
He will be arraigned on charges of armed robbery, assault and battery, and assault and battery with a risky weapon.
The student was treated at a hospital.
One suspect is described as a white male wearing a dark-colored shirt and gold chain.
During a news conference late Friday morning, UMass Police Chief Tyrone Parham said they issued a warrant for the arrest of their primary suspect, who he declined to identify.
The order was lifted shortly after 7 p.m.
That dormitory is one of the low-rise dorms in the university’s Southwest residential area.
A shelter-in-place was ordered for the entire campus.