RUSTON, La. (AP) — Four people were stabbed Monday morning on the campus of Louisiana Tech University in the north Louisiana city of Ruston.

The university issued a statement saying campus police caught a suspect — a 23-year-old student named Jacoby Johnson — within minutes of the stabbings. The student was being treated for unspecified injuries and had not been formally charged as of midday.

The attack happened shortly after 9 a.m. at Tech’s Lambright Sports and Wellness Center, a recreation center for students and the Ruston community. Tech police received a call at 9:08 and the suspect was reported in custody around 9:12, the university said.

Of the four people stabbed, one was a graduate student, who was reported in serious but stable condition after being airlifted to a Shreveport hospital. The other victims were not students. Two were at the hospital in Ruston, one in serious condition; the other, critical. A fourth victim refused treatment.

“This appears to be a random act of violence,” the university’s statement said. “It sounds like he ran up behind them and surprised them,” Ruston Police Chief Randall Hermes told the Ruston Daily Leader.