Four adults and a 7-year-old boy were killed Thursday in Ontario after an out-of-control car drove off the 10 Freeway and hit another vehicle near an exit ramp, officials said.
Michael Pineda, a boy who was riding in the out-of-control Toyota Yaris, died in a nearby emergency room, the San Bernardino Sheriff's Department said Friday.
All four people in the other vehicle, a Toyota Solara, died at the scene, authorities said. They were identified as: Matthew Pusateri, 29, of Mission Viejo; Anthony Flores, 30, of Hemet; Jeffrey Willey, 29, of Huntington Beach; and Monica Flores, 37, of Arcadia.
The crash occurred shortly after 7 p.m. Thursday, sheriff's officials said, after the Yaris "began to accelerate uncontrollably" while driving east on the 10 Freeway.
The driver, "unable to stop or slow the car," drove off the freeway at the Vineyard Avenue exit, the sheriff's department said. It then struck the second car, a sedan driving north on Vineyard.
The California Highway Patrol is investigating the crash.
CHP Officer Christina Wood said Friday that investigators do not believe the 51-year-old woman driving the Yaris was under the influence of alcohol or drugs. The driver, Wood added, was "fully cooperating" with investigators.
The driver, along with a 16-year-old boy and 12-year-old girl who were passengers, were still at Loma Linda University Medical Center on Friday, Wood said, where they were being treated for their injuries.
Wood said the driver was related to the 7-year-old boy who was killed in the crash, but did not specify how.
The two people sitting in the front of the Solara were wearing their seatbelts, Wood said. Investigators have not been able to determine whether the two people in the backseat were, she said, because of the damage to the vehicle.
Times staff writer Soumya Karlamangla contributed to this report.