A Suffolk County deputy sheriff's car patrolling the Long Island Expressway struck and killed an 18-year-old Wednesday in Ronkonkoma after the teenager stopped his car in the high-occupancy lane and got out of the vehicle, officials said.

The deputy sheriff was traveling west near Exit 59 at 5:49 p.m., officials said, and his vision was compromised by glare from the setting sun.

Michael Sharkey, chief of staff for the Sheriff's Office, said, "There was sun glare and our deputy attempted to avoid the vehicle, and the operator was in the road."

CPR was performed on the teenager, William Schettino of Blue Point, while he was being taken to Stony Brook University Medical Center, but he was pronounced dead there a short time later. The deputy sheriff, whose name was not released, was also taken to a hospital, but his injuries are not believed to be serious, Sharkey said.

All westbound lanes were closed immediately after the accident at Exit 59 and remained closed past 11 p.m. to facilitate the police investigation.

A man who said he was Schettino's grandfather said in a phone interview that Schettino had a mishap before being hit by the deputy sheriff and ended up on the HOV lane.

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"He was sideswiped and driven into the HOV lane," he said. "He couldn't get out of the driver's side so he got out of the passenger's side, after he put his lights on, after he contacted the police department."

Sharkey said yesterday that it is not known why the car, a 2011 Mazda, was stopped in the HOV lane, or why the driver decided to leave the vehicle.

"I would like to stress to people that if something happens to their car, and they're not able to move it out of the roadway, the safest thing to do is stay in the car with your seat belt on and call 911," Sharkey said. "Obviously, if you can get it out of the roadway, you should."

-- With Ellen Yan