SAN PEDRO (CBSLA.com) — Police Friday were investigating the cause of a fatal crash involving a vehicle that plunged into the Port of Los Angeles.

A Honda carrying a family of four left a parking lot at the Ports O’ Call Village in San Pedro around 6:10 p.m. Thursday, then ran off the road at Berth 73, according to the Los Angeles Fire Department.

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The father, Ali Elmezayen, told police he accidentally hit the gas instead of braking when the vehicle flew off the pier and overturned in water approximately 30 feet deep, LAPD Sgt. Green said.

Elmezayen and his wife were able to escape and swim to the surface to call for help for two boys — ages 13 and 8— who were trapped in the submerged vehicle.

LAFD rescue divers were able to free the boys, who were not breathing when they were pulled out of the water.

Both were transported to a local hospital where the 13-year-old was pronounced dead two hours later.

The 8-year-old’s condition was upgraded Friday morning from grave to critical. He remained in the ICU.

The adults were treated and released from a hospital.

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Crews pulled the family’s vehicle out of the water around 2:30 a.m.

Although the LAPD initially said the incident was being considered an accident, detectives were looking into “a whole realm of possibilities,” Sgt. Dana Adams said.

Witnesses said they say Elmezayen emerge immediately from the water after the car went over the edge of the road, swim to a ladder and stay there. His wife emerged about a minute later, screaming for help, witnesses said.

Commercial fisherman Ray Perez said he and other witnesses yelled at Elmezayen to go help his kids and his wife.

“He just stood there,” Perez said.

Other witnesses told police they heard the couple arguing just before the car went into the water.

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The crash remains under investigation.