From WashingtonPost.com

If all went according to procedure, Prince George’s County sheriff’s deputies would have arrested Deangelo Walker just hours before he is thought to have fatally shot a neighbor in Capitol Heights, authorities said.

On Sept. 19, deputies tracked down Walker, 30, and served a peace order mandating that he stay away from a man who accused him of throwing a coffee mug at his wife and daughter. The deputies let Walker go on his way, failing to arrest him on a warrant charging him with second-degree assault.

That night, police said, Walker fatally shot William Albert Nelson, 47. Walker has been charged with first-degree murder.

Sheriff’s officials acknowledged the slip-up, first reported by The Washington Times, and said they are investigating the incident. If deputies had followed protocol, the arrest warrant would have been served with the peace order, and Walker would have been jailed, said Sharon Taylor, a spokeswoman for the Prince George’s County sheriff’s office.

Walker has a history of run-ins with neighbors and the law, according to authorities and court records.

Aaron Smith, one neighbor, had sought the arrest warrant Aug. 30, alleging that Walker had broken into residents’ cars and thrown a coffee mug at his wife and daughter.

A court issued the warrant, but it went unserved for weeks, records show. Taylor said that because the charge was second-degree assault — a misdemeanor — the warrant wasn’t immediately given high priority. Deputies upgraded its status after learning that Walker had a history of mental issues and violence, including an assault conviction, Taylor said.

“His troubled past sort of put a spotlight on him,” she said.

On Sept. 19, Smith obtained the peace order citing similar allegations. Deputies served it about 7 p.m. that day — about two hours before the slaying, Taylor said.

Deputies served the assault warrant about 6 a.m. the next day, she said. Walker had not been charged with murder at the time, and deputies did not know he was a suspect, Taylor said.

Warrant service has been of concern in Prince George’s County, and Sheriff Melvin C. High has touted efforts to reduce a backlog that stood at more than 50,000 earlier this year. At a news conference last week, High said the backlog was down to about 47,400 , and deputies are now able to manage new felony warrants and clear old ones.

The recent oversight is not the first for the sheriff’s office. A teenager accused of killing a man in Forestville during a domestic dispute in January had been charged with attempted murder in 2009, but sheriff’s deputies did not serve that arrest warrant until after the slaying.

Smith said he is frustrated that law enforcement did not seem to heed his warnings. “If they would have arrested him that day with the assault,” he said, “then that man wouldn’t have been killed.”

Efforts to reach the families of Walker and Nelson were unsuccessful.