Suffolk County police internal affairs detectives are investigating the death of a West Islip man in custody Friday, after he had to be revived from a crash when police believed he was driving under the influence of drugs.

Police said Joseph Leonard, 58, was driving a 2016 Jeep Wrangler at 5:30 p.m. Thursday when he rear-ended a car stopped at a red light on Pine Aire Drive at Fifth Avenue in Brentwood.

When police arrived, they found Leonard unconscious behind the wheel. Police administered Narcan, an opioid overdose reversal drug.

Paramedics with Brentwood Legion Ambulance took Leonard to South Shore University Hospital in Bay Shore, where he was arrested and charged with driving while ability impaired by drugs and two counts of criminal possession of a controlled substance.

He was released into police custody and held overnight at the Suffolk County police Third Precinct in Bay Shore.

Police said they found Leonard not breathing at 9 a.m. Friday when they were preparing to take him to his scheduled court appearance. Officers attempted first aid, but Leonard was pronounced dead at the precinct. police said.

The Suffolk County Homicide Squad and Internal Affairs Bureau is investigating the death, with the New York Attorney General’s Office. The Suffolk County medical examiner is planning an autopsy to determine the cause of death.

Family members and an attorney for Leonard could not be reached for comment Friday evening.

PLUS: Where to get holiday pies Credit: Newsday

Navigating politics over Thanksgiving and where to get holiday pies. Here's a look at some of the exclusive stories you may have missed this week on NewsdayTV.

PLUS: Where to get holiday pies Credit: Newsday

Navigating politics over Thanksgiving and where to get holiday pies. Here's a look at some of the exclusive stories you may have missed this week on NewsdayTV.

SUBSCRIBE

Unlimited Digital AccessOnly 25¢for 6 months

ACT NOWSALE ENDS SOON | CANCEL ANYTIME