A student shot and killed three people and left another three injured, before turning the gun on himself, telling an onlooker "today is my last day".
Ali Syed, a 20-year-old part-time student in Orange County, California, is believed to have gone on a killing spree in the early hours of Tuesday morning, according to USA Today.
Californian police identified Syed as the gunman, but say it is still not clear what his motives are. The student started his rampage at his home in Ladera Ranch, about 30 miles from Los Angeles shortly before 4.45am. Police were called to the scene and found the body of an unidentified woman riddled with bullets.
Syed, a pupil at Saddleback College, then stole a series of cars and killed two others, Tustin Police Department said. The student also injured three more in the 25 minutes of bloodshed.
One carjacking victim said Syed had pointed a gun at him and asked for his keys, telling the victim: "I don't want to hurt you. I just killed somebody and today is my last day."
One driver was ordered out of his BMW and shot dead in front of horrified onlookers, the BBC reported. "He was basically executed,'' a Santa Ana police spokesman said.
Officials attempted to stop Syed but the student shot himself inside a car before police could reach him.
"I do not believe any of the victims are related to each other. It might have been a random thing," Orange County sheriff's spokesman Jim Amormino told KNBC-TV. "We just don't know."