Two of the wounded were transported to a hospital by helicopter and others were treated on campus.
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.
However, authorities did not release the name of the assailant or his victims.
Police said that two of those stabbed are students at the school and the two other victims are a staff member and a contract employee.
Motive behind the attack was not detailed and it is unclear whether there is a relationship between the assailant and the victims, said James Leonard, a school spokesman.
The incident began when the assailant used a knife to stab two people in a second-floor room around the start of an 8 a.m. class, Merced County Sheriff Vern Warnke said.
The contract employee went into the classroom to help and “ended up stumbling upon the stabbing in progress,” Warnke said. “I think, through his actions, that he ended up saving this student’s life.”
Authorities are investigating a motive. Warnke said the knife contained a blade that was eight to 10 inches long.
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