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 —within minutes of the stabbings. The student was being treated for unspecified injuries and had not been formally charged as of midday.

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.

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.