A man found dead Thursday afternoon under a pile of snow in Southeast Washington had been in and out of St. Elizabeths Hospital for nearly 30 years and had left the District’s psychiatric hospital without permission Feb. 9, according to authorities and public records.

An investigation is underway to determine how Daniel Ellis, 56, managed to walk away from the hospital undetected. Officials said Ellis had been voluntarily committed and was allowed to be in his building’s lobby and on the grounds as long as staff members were present.

“We are reviewing what happened and seeing if staff followed proper procedure or there was a breakdown in our protocol,” said Phyllis Jones, the spokeswoman for the District’s Department of Behavioral Health, which runs St. Elizabeths. She said a supervisor filed a missing person report with D.C. police after they noticed that Ellis was missing.

Because Ellis’s latest stay at the hospital was voluntary and not due to a court order or a crime, he was free to sign himself out and leave. But Jones said the hospital could have held him involuntarily for 48 hours to make sure that he had his medication and a place to go.

“We definitely would have discouraged him from leaving,” Jones said, adding that any discharge would have been “against medical advice.”

Had staff noticed him leaving, Jones said, “we would have stopped him.”

Ellis’s body was found about 12:45 p.m. Thursday in the 2400 block of Shannon Place SE, a residential street about two miles from the hospital. Police did not give any details on who found the body or under what circumstances. Police did say that the body was covered with snow.

Ellis’s family could not be reached Friday, and D.C. police said the medical examiner had not ruled on how he died or whether the snow, ice and cold contributed to his death.

The discovery came as District residents shoveled out from more than eight inches of snow. CNN’s Wolf Blitzer asked D.C. Mayor Vincent C. Gray (D) about the death during an interview Thursday, and the mayor confirmed that the man had been a patient at St. Elizabeths.

“He apparently had wandered away from there several days ago, and we are still obviously learning more about this,” Gray told Blitzer. “We’ll find out what happened, why he was away from the hospital and how he wound up in these conditions.”

Court records show that Ellis has a long history of run-ins with authorities. Court records associated with many of his arrests — mostly involving petty crimes — quote doctors saying Ellis had been a patient at St. Elizabeths “almost continuously” since 1985 and had received a diagnosis of schizophrenia.

Many charges filed against Ellis dating to the early 1980s were dismissed because doctors repeatedly found him incompetent to stand trial, according to court records. He does have several felony convictions, most for assault.

One of the later assault cases occurred at St. Elizabeths in 2008, when he was arrested and charged with hitting a hospital staff member 20 times in the face with a closed fist, according to court documents. Ellis told authorities that he wanted to leave but that the doctor wouldn’t let him, according to the documents. A doctor at St. Elizabeths found him incompetent to stand trial in that case.

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