US media report that the gunman who killed three people at the University of Nevada in Las Vegas UNLV, was an academic who applied for a job at the school but not hired.
The suspect, described as a white former college professor in his 60s, was killed in a shootout with police.
Officials have so far not released his name, but CBS News has identified him as Anthony Polito.
Police have not named the victims, but media reports say none were students.
Investigators at the state, local and federal levels are currently digging into what drove the Wednesday shooting, which also injured one person.