Robert W. Richards, a former sergeant who helped provoke international outrage when he and three other Marines were seen on videotape urinating on the corpses of Taliban fighters in Afghanistan in 2011, died on Wednesday at his home in Jacksonville, N.C., near Camp Lejeune, where he had once been based. He was 28.

His lawyer, Guy Womack, confirmed the death, saying there were no signs of foul play or self-inflicted wounds, The Associated Press reported. Mr. Womack said he suspected that a combination of medications that Mr. Richards had been taking for combat injuries and post-traumatic stress disorder contributed to the death.

Mr. Richards pleaded guilty at a court-martial at Camp Lejeune in August 2013 and was demoted to corporal. He was granted a medical retirement with an honorable discharge.

At the trial, one Marine testified that his comrades believed that the dead Taliban fighters had been responsible for the roadside bombing death of a platoon sergeant earlier that day. Eight Marines have been punished for their involvement in the episode.