A male student armed with a hunting knife stabbed four people on Wednesday, Nov 05, before he was shot dead by campus police at the University of California, Merced, in the heart of the state’s Central Valley, law enforcement and school officials said.

The attack occured at outside the university’s Classroom and Office Building.

The attacker burst into a morning class to kill his intended victim, and may have, had it not been for the heroic intervention of a construction worker who ran into the room to break up the attack.

The construction worker and three others were injured, but all are expected to survive. The alleged assailant, described as a college student in his 20s, was shot and killed by campus police as he fled the scene at the University of California, Merced.

All those attacked at the University of California, Merced, were conscious when paramedics reached them, Assistant Vice Chancellor Patti Waid said.

Two victims were airlifted to a local hospital while three were treated at the scene. Niether the suspect or victims have been identified.

Police said the assailant was a student but had not confirmed his identity or provided a motive for the attack. Officials said they were still working out a timeline of events leading up to the stabbings, and it wasn’t clear how the attack played out.

The stabbings come about a month after a gunman killed nine people and himself at a college in Oregon, in the deadliest of dozens of U.S. mass shootings over the past two years.