On month after shooter Elliot Rodger went on a killing spree in Santa Barbara, the FBI is formally investigating the Santa Barbara Sheriff's Department for a welfare check they did on Rodger before the massacre, Breaking Celebrity News has learned exclusively. Could he have been stopped?

Three weeks before Elliot Rodger went on his shooting spree, sheriff's deputies made a welfare check to his Santa Barbara apartment, after his mother, Li Chin, became concerned that her troubled son might attempt to commit suicide.

Authorities said that during an April 30 check-in call they made to Rodger’s apartment, they did not search his domicile for firearms he had on hand at the time, as they did not consider him a serious threat.

The FBI opened the "investigation almost immediately after the tragedy occurred,” a source with knowledge of the situation told Breaking Celebrity News. "The investigation is focused on the SBSD's handling of the home welfare check of Elliot, and that they had failed to watch videos he had made. It's going to be a very thorough and exhaustive investigation. The FBI has also been in contact with all of Elliot's doctors and various health care professionals, and subpoenas have been issued for copies of his medical records."

In a 137-page manifesto Rodger sent to family and friends before the rampage, he described his panic at the deputies’ visit, fearing they had been tipped off to his plot.

“The police would have searched my room, found all of my guns and weapons, along with my writings about what I plan to do with them. I would have been thrown in jail, denied of the chance to exact revenge on my enemies. I can’t imagine a hell darker than that. Thankfully, that wasn’t the case, but it was so close," Elliot revealed.