Four people were killed and nine others were injured Saturday when a suspected drunk driver lost control of his pickup truck, plunged off the San Diego-Coronado Bridge, and plowed into a crowd gathered at a festival below, authorities said. 

The California Highway Patrol said the driver, 25-year-old Richard Anthony Sepolio, struck a guardrail and fell 60 feet before landing on a vendor booth set up for a motorcycle festival in Chicano Park. Sepolio was taken to the hospital with major injuries and will be arrested on suspicion of driving under the influence causing deaths and injuries, California Highway Patrol Officer Jake Sanchez said.

Authorities said Sepolio is an active-duty member of the U.S. Navy stationed at a base in Coronado Island, across a bay from San Diego.

The names of the deceased victims were not immediately released, but authorities identified them as a 62-year-old man and 50-year-old woman from Chandler, Ariz., and a 59-year-old man and 49-year-old woman from Hacienda Heights, a suburb east of Los Angeles. Witnesses said all four victims were in the vendor booth that was crushed by the truck.

"It's horrible. It's horrific. We had innocent people down here having a good time and now they're gone," Sanchez said.

Eight people on the ground were injured. One suffered major trauma and seven others had minor to moderate injuries, said Lee Swanson, a spokesman for the city's Fire-Rescue Department.

The vendor booth was set up for La Raza Run, a motorcycle ride that ends with a celebration at the park and typically draws hundreds of participants. The crash occurred in front of a stage where a rockabilly band was playing.

"I saw a truck come right off the freeway. It was going so fast it flew over the stage and landed in front of the stage on a tent, a booth that was set up," Chase Dameron told The San Diego Union-Tribune .

He said four people in the booth were crushed by the truck.

"It was like a movie. It was like in slow motion," Dameron said. "Where it hit, there was dust and debris and instant chaos and panic. People running crazy."

Photos from the scene show the truck's front end was crumpled and its hood popped open.

The park is located beneath the bridge in a predominantly Hispanic neighborhood in central San Diego.

The Associated Press contributed to this report.

Click for more from Fox 5 San Diego.