Santa Barbara County Sheriff Bill Brown said some of those killed or injured in Friday night's Isla Vista shooting rampage may have been struck by the suspect's vehicle.
"It's a combination of people suffering from gunshot wounds and others who received some traumatic injuries that ... may have been struck by the vehicle," Brown said.
Authorities are reviewing evidence that suggests the series of drive-by shootings that left seven people dead, including a man believed to have carried out the attacks, was "premeditated mass murder," Brown said at a Saturday morning news conference.
Brown called the shootings in Isla Vista near UC Santa Barbara "horrific" and said officials are investigating a "chaotic series of crime scenes."
Nine separate crime scenes have been identified in the area, said Brown, who described the drive-by slayings as "the work of a mad man."
The man believed to be the shooter was found dead inside his vehicle with a gunshot wound after engaging in two separate gunfights with deputies, the Santa Barbara County Sheriff's office said. It's unknown if the gunshot was self-inflicted or if the suspect was shot by authorities.
A semi-automatic handgun was recovered inside the vehicle, Brown said.
The man has been preliminarily identified, but his name hasn't been released pending positive identification, authorities said. Investigators believe he acted alone and they're currently analyzing video and written evidence that suggests the killings were premeditated.
One YouTube video, titled "Elliot Rodger's Retribution," appears to be connected to the crime, Brown said. The video has been taken down from the site. "We're investigating that as evidence we believe is connected."
The video appears to have been done by a young man who identified himself online as a student in Santa Barbara.
"I'll take great pleasure in slaughtering all of you. You will finally see that I am in truth the superior one, the true alpha male," the man says on the video, sitting in a car.
On the six-minute video, he talks about feeling alienated and rejected by women.
"I will be a god compared to you. You will all be animals. You are animals, and I will slaughter you like animals. I hate all of you. Humanity is a disgusting, wretched, depraved species," he says.
"Yes, after I have annihilated every single girl in the sorority house I'll take to the streets of Isla Vista and slay every single person I see there."
On a Google+ profile for Elliot Rodger linked to the YouTube video, Rodger is presented as a "Political Theorist, Philosopher, Writer."
"I consider myself a sophisticated, polite gentleman, unlike most boys my age," according to the Google+ profile.
The deadly shootings started at 9:27 p.m. in Isla Vista. As deputies were tending to the injured in the first round of shootings, reports of gunfire in several other areas of the college community were reported.
Six minutes after the first 911 call came in, the unidentified man began shooting at deputies, who returned fire. He fled and seconds later was spotted by another deputy, prompting another firefight.
He then took off down Del Playa Drive and crashed into a parked vehicle, the sheriff's office said. When deputies approached the vehicle they discovered the man was dead and they recovered a semi-automatic handgun.
The seven injured people are being treated for gunshot wounds or traumatic injuries; their conditions are unknown. At least one of them has undergone surgery.