A former Brentwood man awaiting trial for second-degree murder died Friday in the Suffolk County jail in Riverhead, the sheriff’s department said.

Tommy Bisbal, 40, was found dead in his cell, said Michael Sharkey, chief of staff for the sheriff’s department.

The cause of death won’t be determined until an autopsy is done, but Sharkey said he believed it to be related to a medical problem.

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Bisbal and his girlfriend, Sabrina Hornoff, 43, were charged with luring rival drug dealer Felix Hidalgo Jacquez from the Bronx to Medford in July 2012. Suffolk prosecutors said the couple intended to rob Hidalgo, but instead Bisbal shot him to death and set him on fire.

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Although Hornoff remains charged with murder, prosecutors don’t believe she took part in the killing. She is now free without bail and living in Florida, but was expected to return to testify against Bisbal. She is due back in court next month and likely will plead guilty to a lesser charge, said her attorney, Daniel Russo of Westhampton Beach.

“No one ever believed she had a role in the killing,” Russo said.

The couple’s then-7-year-old daughter was present for the aftermath, prosecutors said. They were also charged with endangering the welfare of a child.

Hidalgo was shot with a .32-caliber handgun in his sport utility vehicle in an office building parking lot.

Video surveillance recorded at nearby gas stations shows Bisbal driving Hidalgo’s car — probably with Hidalgo’s body in the back seat — and filling a container with gasoline before heading toward where the burning body was found, prosecutors said after the couple was indicted. Other video footage shows the couple’s car, with their child visible in the back seat, they said.