A Patchogue man who pleaded guilty in February to killing another motorist while he was high on prescription drugs and PCP in 2013 has died while being held in the Suffolk jail, officials said Tuesday.

Thomas Herman, 48, whose plea led to his conviction on a charge of first-degree manslaughter in the death of Sam Longo, 82, of West Islip, was found unresponsive in his cell at the facility at about 8 a.m. Sunday, Chief Michael Sharkey said.

Sharkey said Herman was taken to Peconic Bay Medical Center, where he was pronounced dead. Sharkey said the death was likely due to natural causes.

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Officials at the state Commission of Correction, which oversees all correctional and detention facilities in the state, was notified within hours of the death and will be investigating it, as the agency does in all deaths, a spokesman said.

Herman's attorney, William Keahon of Hauppauge, also confirmed his client died in the Riverhead jail. The death comes a month before state Supreme Court Justice Mark Cohen was to sentence Herman to 21 years in prison on May 15.

Herman had admitted in court to speeding in his 2008 Chevrolet Trailblazer on Montauk Highway in Sayville on Jan. 13, 2013, when he hit several cars before crashing head-on into Longo's vehicle.

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The crash also seriously injured Longo's passenger, Agnes Gilbert of Oakdale, who was 80 at the time.

Suffolk prosecutors originally charged Herman with second-degree murder but later said the victims' families had consented to the guilty plea.