A white man who shot three young black men who had been trying to evacuate in the aftermath of Hurricane Katrina died just days after being sentenced to 10 years in prison for the crimes, the authorities said Wednesday.

The man, Roland J. Bourgeois Jr., 56, died Feb. 19 — five days after his sentencing — at a jail in Louisiana while he was in the custody of the United States Marshals Service, Walter Martin, a supervisory deputy, said. Mr. Bourgeois had been awaiting a transfer to a federal prison.

The Plaquemines Parish Sheriff’s Office is handling the death investigation, Mr. Martin added. The cause of death was not immediately clear, but Mr. Martin said the authorities did not suspect foul play.

Federal prosecutors had cited Mr. Bourgeois’s physical and mental health as one reason his court proceedings dragged on for nearly nine years after he was initially indicted. During that time, Mr. Bourgeois was repeatedly found incompetent to stand trial. He was eventually declared competent in 2018.