The violent rampage in Isla Vista, California, that killed six people?- three of them shot to death?- has US politicians calling for tougher controls to keep guns out of the hands of people with a history of mental illness.

Elliott Rodger, 22, the man police say was behind the deadly attacks at Isla Vista near UC Santa Barbara on the night of May 23, was able to legally obtain three guns despite a history of depression and having been under the care of a therapist for some time.

Experts said that under California's gun control laws, getting treatment would not have prevented Rodger from legally obtaining the three guns he used.

California US Senator Dianne Feinstein, a Democrat, said that Rodger was able to purchase multiple handguns despite a history of mental instability serves as a stark reminder that there needs to be further limits to who can buy guns.

US Senator Richard Blumenthal, a Democrat from Connecticut, said the Isla Vista rampage had pushed him to renew efforts for legislation aimed at keeping guns out of the hands of "dangerous” individuals.

In an interview on CBS's Face the Nation on May 25, Blumenthal said gun-control bills could be reconfigured "to center on mental health, which is a point where we can agree that we need more resources to make the country healthier and to make sure that these kinds of horrific, insane, mad occurrences are stopped.”

Republican New York Representative Peter King, a gun-control supporter, told the Washington Post May 24 that the Isla Vista rampage demonstrated "once again the need to keep guns out of the hands of the mentally ill.”

Richard Martin, father of Chris Martinez, 20, who was shot to death at a deli in the rampage, lashed out at politicians and the National Rifle Association for blocking tougher gun legislation.

"Chris died because of craven, irresponsible politicians and the NRA. They talk about gun rights. What about Chris's right to live?" Richard Martinez told reporters the day after the violence occurred.

"When will this insanity stop? When will enough people say, 'Stop this madness!' We don't have to live like this. Too many have died. We should say to ourselves, 'Not one more!'"

In addition to Martinez, Rodger shot two women to death outside a sorority house and stabbed to death three Chinese students in his apartment, police said. He then went on a shooting rampage from his car, wounding 8 people before apparently killing himself investigators said.

Adam Winkler, a UCLA law professor and expert on gun laws, said that, in general, a diagnosis of mental illness doesn't affect a person's right to own a gun in California unless the matter has been adjudicated by a court or the person has voluntarily checked into a mental facility.

"It's just not a surprise that someone with mental health problems would still be able to get a gun," Winkler told the Los Angeles Times.