LITTLE ROCK, Ark. (AP) — A pathologist fired from an Arkansas veterans hospital after officials said he had been impaired while on duty was charged Tuesday with involuntary manslaughter in the deaths of three patients who authorities say he misdiagnosed and whose records he later altered to conceal his mistakes.

A grand jury indictment unsealed Tuesday charged Dr. Robert Morris Levy in the patients’ deaths and on multiple charges of fraud and making false statements for his alleged attempts to conceal his substance abuse and incorrect diagnoses.

“In doing so, he was allowed to stay employed with the Veterans Administration, thus earning a salary, benefits and possibly a bonus,” Duane Kees, the U.S. Attorney for the Western District of Arkansas, said at a news conference in Fayetteville, referring to the Department of Veterans Affairs by its former name. Levy, who worked at the Veterans health Care System of the Ozarks in Fayetteville, was paid an annual salary of $225,000, according to the indictment. He was fired from the hospital in April 2018.

VA officials said in January that outside pathologists reviewed nearly 34,000 cases handled by Levy and found more than 3,000 errors or missed diagnoses dating back to 2005. Levy has acknowledged that he once showed up to work at the Veterans Health Care System of the Ozarks drunk in 2016, but he denied that he had worked while impaired. He entered an in-patient treatment program following that incident and returned to work in October 2016 after agreeing to remain sober and submitting to random drug testing.

Levy, who was being held at the Washington County jail, pleaded not guilty at a hearing Tuesday. Kees said that as of Tuesday morning, Levy had not obtained counsel to represent him in the case.

In the deaths, Levy is accused of falsifying entries in his patients’ records after making incorrect and misleading diagnoses. In one case, a patient died of prostate cancer after Levy determined that his biopsy showed he didn’t have cancer, prosecutors allege.