Santa Barbara Massacre -- Shooter Vows to Kill Out of Sexual Frustration

The horrific massacre at UCSB Friday night -- in which 6 people were shot dead -- seemed to be triggered by a maniac who was angry at women because they would not have sex with him ... and TMZ has learned shooter has a connection to "Hunger Games."

22-year-old Elliot Rodger posted a YouTube video hours before he unleashed his violence on the streets of Isla Vista -- the UCSB community. We've learned Rodger is the son of Peter Rodger, the second unit director of the first installment of "Hunger Games."

Elliot Rodger was killed as he engaged Sheriff's deputies who responded to the scene. He died from a gunshot wound to the head, although it's unclear if it was self-inflicted.

In the video you hear Rodger's fury at the women who did not find him attractive and you hear his resolve at getting revenge.

According to reports ... a lawyer for Peter Rodger says the director contacted police several weeks ago about YouTube clips his son had uploaded in regards to "suicide and killing people."

The Associated Press says the lawyer claims police interviewed Elliot and found him to be a "perfectly polite, kind and wonderful human."

"My client's mission in life will be to try to prevent any such tragedies from ever happening again," the lawyer said. Adding, "This country, this world, needs to address mental illness and the ramifications from not recognizing these illnesses."