A pickup truck swerved off a bridge and plummeted about 60 feet crashing into a crowd below who had gathered at a San Diego park, authorities said.
Four people died and nine people were injured, including the pickup driver, in the Saturday accident.
The driver, who suffered major injuries, was taken to UC San Diego Medical Center for treatment and also placed under arrest for driving under the influence.
"It was determined that alcohol was involved," said Jake Sanchez, public information officer for the California Highway Patrol's San Diego office.
Around 3:30 p.m., the gray GM pickup truck had been traveling northbound on Interstate 5, and was turning towards the Coronado Bridge when the driver lost control. Police did not have details on the vehicle's speed.
Down below, a crowd had gathered at Chicano Park for a motorcycling event called La Raza Run.
"I looked up and I could see a car flying up in the air," Delores DeAngelo, who had been at the park, told CNN affiliate KUSI. "I could see it flying through the air and I thought, 'It's going to hit me,' and I moved over."
She fell to the ground and heard a big boom.
"All the dust started flying through the air," she said. "I could feel all the dust and dirt flying into my mouth. Pieces of car parts were flying all over the place. When I got up, we turned around and everyone started running over there because we realized there were people sitting there."
When emergency responders arrived on scene, they found the pickup truck on its side, on top of four individuals. Those four died.
One other person suffered major injuries and seven others had moderate injuries, Sanchez said.
"It's horrific," he said. "They were innocent people having a good time."