GREENSBORO, N.C. — The city of Greensboro, North Carolina, some of its police officers and several others are being sued by the parents of a black man who was hogtied and died in police custody last year.

The News & Record reports the lawsuit was filed Wednesday on behalf of Mary and George Smith, the parents of 38-year-old Marcus Deon Smith.

Smith’s autopsy report said he died of cardiopulmonary arrest caused by factors including “prone restraint” by police and a mixture of drugs, alcohol and cardiovascular disease. It ruled the death a homicide.

Former Guilford County District Attorney Doug Henderson determined the officers weren’t criminally negligent in Smith’s death. Their identities haven’t been released.

Mayor Nancy Vaughan says the lawsuit endangers the possible independent investigation into Smith’s death, which officials have been discussing.