LOS ANGELES >> The parents of the first three victims of a deadly rampage outside Santa Barbara last year are suing the county, the Sheriff’s Department and the apartment building where the killer lived, contending they ignored numerous warning signs that he was violent and unstable.

The lawsuit filed Monday in federal court alleges negligence and violations of the victims’ constitutional right to due process.

Elliot Rodger, 22, stabbed, shot and ran down people in the community of Isla Vista on May 23. He killed six University of California, Santa Barbara, students and injured 14 other people before shooting himself as authorities closed in.

His first three victims were his roommates, David Wang and James Hong, and a friend, George Chen, who were stabbed dozens of times with a nearly 9-inch boar-hunting knife. The lawsuit was filed on behalf of their parents.

It contends that authorities, and the apartment building and its owners, ignored numerous warning signs that Rodger was dangerous, including failing to check his online postings in which he spouted venomous comments about women and others and bemoaned his virginity.

After Rodger killed himself, police found three semi-automatic handguns and nearly 550 unspent rounds in his car. All were purchased legally.

The lawsuit names Santa Barbara County, the Sheriff’s Department, Capri Apartments and Asset Campus Housing, a Texas-based company that provides student housing around the nation.

The suit said that after Rodger moved into the Capri complex in 2011, he insulted and clashed with a string of roommates and exhibited bizarre behavior, yet the apartment owners failed to conduct reasonable background checks before assigning Hong and Wang as his roommates. The suit also says the complex failed to warn them that “Rodger had had serious conflicts with his previous roommates and was not only racist but also potentially violent and dangerous.”

It also contends that the county and its Sheriff’s Department violated the victims’ rights to due process by ignoring repeated “red flags” that Rodger was violent and unstable, even after a mental health worker saw YouTube videos that Rodger had posted and contacted authorities to say that Rodger appeared to be a danger to himself and others.

The Sheriff’s Department said in a statement that it could not comment on pending litigation “and anything we might say in response would be insufficient when measured against the grief suffered by the families of those killed so tragically.”

Messages seeking comment from representatives of the county were not immediately returned. The offices of Capri and Asset Campus Housing were closed and messages could not be left there seeking comment.