SEAFORD — A suspect in a Seaford pharmacy robbery and an off-duty federal agent who tried to stop him were both shot and killed Saturday afternoon but the circumstances are still being determined, according to police.

Nassau Detective Lt. Kevin Smith, the department’s chief spokesperson, said that a lone man walked into Charlie’s Family Pharmacy on Merrick Road around 2 p.m. and “he announces a stick up.” The man robbed the store of cash and Oxycontin, a powerful prescription painkiller, Smith said. When he fled the pharmacy near the corner of Jackson Avenue, an off-duty Bureau of Alcohol, Tobacco and Firearms agent, an off-duty NYPD officer and a retired Nassau police officer confronted the suspect, Smith told reporters at the scene, according to the Associated Press.

A “struggle ensued” and the suspect was shot and killed by one of the men, police said. The ATF agent was also shot and was taken to Nassau University Medical Center, where he later died, Smith said.