MALIBU (CNS) - A driver got out of her car on the side of Pacific Coast Highway in Malibu today and was killed — on her 21st birthday — by a hit-and-run motorist, who was arrested in Agoura Hills a short time later, authorities said.

The Van Nuys resident, whose name was withheld pending family notification, was struck about 5:40 a.m. on northbound Pacific Coast Highway at Ramirez Canyon Road. She died at the scene, according to sheriff’s officials from the Malibu/Lost Hills Station.

Three friends who were in the car with the victim provided authorities with a description of the hit-and-run vehicle, said sheriff’s Lt. James Royal.

Deputies then arrested Pablo Carranza, 25, of Pacoima, and he was booked on suspicion of felony hit and run, Royal said.

It was unclear why the woman pulled over and got out of the car. The roadway shoulder is very narrow at that location, and officials cautioned people to be careful when stopping and getting out of their vehicles.

Both northbound lanes of PCH were closed while an investigation was conducted. One lane of the lanes reopened 2 1/2 hours later, and the other reopened by early this afternoon.