Authorities in California have arrested a man on suspicion of intentionally driving into crowds at the Venice Beach boardwalk, killing a woman and injuring 11 others in a bloody scene that witnesses described as horrifying.  Los Angeles police say 38-year-old Nathan Campbell has been booked for investigation of murder and remains jailed Sunday on $1 million bail.  He turned himself about two hours after the attack that occurred at around 6 p.m. Saturday. Investigators don't yet have a motive.  Security video shows a man parking his black car alongside the seaside boardwalk as the sun sank, surveying the idyllic scene for several minutes before getting back into the car and speeding into the crowd. It shows hundreds of people walking lazily or sitting at cafes before the black car suddenly appears and sends them scrambling wildly. The car swerved around yellow poles meant to prevent cars from getting into the pedestrian-only area and onto the boardwalk.  One witness told CBS LA that the driver was "out for blood." Another estimated that the car was going 60 miles per hour.  I was half a mile from the scene, but you could see just this mass of people trying to get out of the way," witness Daniel Regidor told the Los Angeles Times. "Just a lot of people screaming ... It was horrible."  A coroner's investigator told City News Service that the woman who died is 32-year-old Alice Gruppioni of Italy.  "There was people kind of stumbling around, blood dripping down their legs looking confused not knowing what had happened, people screaming," said 35-year-old Louisa Hodge, who was out enjoying the day on the boardwalk with a friend visiting from San Diego. "It was blocks and blocks of people just strewn across the sidewalk."  "I heard a big 'boom, boom,' like the sound of someone going up and down the curb, it was super loud," said Alex Hagan, 22, who was working the desk at the Cadillac Hotel and watched the scene unfold from the start.  The driver knocked over two mannequins then started hitting people, swerving from side to side and often running straight into them. The car hit at least three vendors who were sitting at their sales booths, video showed. Two women who were hit appeared to be in their 60s, Hagan said, adding that many ran after the car, screaming and cursing as it sped away.  Hodge saw one man and woman lying next to each other, wearing head braces and barely able to move.  "They were just laying next to each other and grasping hands," Hodge said, "just a man and a woman holding hands."  The driver fled the scene and about an hour later, just as police were circulating word that they were seeking a black Dodge with a driver in his 20s, Campbell walked into a police station in neighboring Santa Monica and told officers he was involved in the boardwalk incident, Los Angeles police Lt. Andy Neiman said.  Police then found a car nearby that they believe belonged to Campbell, Neiman said.  Hours later police were surveying the same stretch of ground for evidence.  The Venice boardwalk is a cultural hub in a part of Los Angeles known for its circus-meets-gritty-city eccentricities.  The 1.5-mile ribbon of asphalt that runs along the sand a few hundred yards from the ocean is home to galleries, restaurants, tattoo shops, skateboard parks and the famous outdoor weight room known as Muscle Beach.  It can draw as many as 150,000 people on summer weekends.  The Associated Press contributed to this report.
A car drove into a packed Saturday early evening crowd walking along the Venice Beach boardwalk in Los Angeles, injuring at least a dozen people, two of them critically.