(CNN) -- Seven people, including a suspected gunman, died in drive-by shootings Friday night in a small Southern California college town, a rampage that authorities believe to be "premeditated," Santa Barbara County sheriff's deputies said Saturday.
The shootings occurred in Isla Vista near the University of California-Santa Barbara. Seven people also were being treated in a hospital for gunshot wounds or traumatic injuries, including at least one who was in surgery, said sheriff's office spokeswoman Kelly Hoover.
"The sheriff's office has obtained and is currently analyzing written and video evidence that suggests this was a premeditated mass murder," Hoover said.
The violence began and ended within minutes, from 9:27 p.m. when shots were reported to around 10 minutes later when police discovered the body of the suspected gunman, CNN affiliate KEYT-TV said.
"Sheriff's deputies responded and found several victims suffering from gunshot wounds. As sheriff's deputies were attending to the victims and performing first aid, they were also receiving suspect information. Only minutes later, there were additional reports of shots fired in several other areas of Isla Vista," Hoover said.
KEYT reported that "witnesses described seeing a black BMW speeding through the streets, spraying bullets at people and various targets." Six minutes after the first emergency call, the suspected gunman traded fire with sheriff's deputies, and the vehicle plowed into a parked vehicle, Hoover said.
The suspected gunman was found dead from an apparent gunshot wound, she said, adding that it wasn't clear whether the death was self-inflicted or whether deputies killed the suspected gunman. A semiautomatic handgun was recovered, she said.
It appears the suspect acted alone, Hoover said.
"This is a very active and complex investigation involving approximately nine different crime scenes," she said.
Santa Barbara Sheriff Bill Brown called the suspect "severely mentally disturbed," according to KEYT.
Authorities searching for a motive were looking into a video posted on social media that contains a man's tirade against women who supposedly rebuffed him, Brown told the station. Hoover said the suspect has been preliminarily identified but his name won't be released until "a positive identification is made."
The identities of the victims won't be released until the next of kin are notified, she said.