“This indictment should remind us all that this country has a responsibility to care for those who have served us honorably,” Duane Kees, the United States attorney for the western district of Arkansas, said in a statement. “When that trust is violated through criminal conduct, those responsible must be held accountable. Our veterans deserve nothing less.”

In addition to the manslaughter charges, a federal grand jury indicted Mr. Levy on 12 counts of wire fraud, 12 counts of mail fraud and four counts of making false statements.

In 2016, Mr. Levy was suspended after being found to have a blood alcohol content of .396 while on duty. He returned to work months later after completing a treatment program and agreeing to abstain from “alcohol and other mood-altering substances” while submitting to random drug tests, according to the indictment. He was suspended a second time in October 2017 after the hospital said he worked under the influence again, and he was dismissed in April last year.

Prosecutors said Mr. Levy had been consuming 2-methyl-2-butanol, a chemical substance known as 2M2B that has an intoxicating effect but is not detectable in routine drug testing.

At a news conference on Tuesday, Mr. Kees strongly cautioned against anyone getting any ideas of abusing the substance. It is extremely dangerous, with “a very minute difference between using it successfully and fatally,” he said.