Police in Maryland said Tuesday that a 27-year-old man accused in the fatal shooting of his stepfather, a District of Columbia police detective, has surrendered to authorities.

Prince George’s County police said Tuesday evening that Antwan James surrendered and was being held at police headquarters. He is accused of killing 46-year-old D.C. police Detective Joseph Newell on Monday night following a dispute over yard work at their home in Upper Marlboro, Md.

Authorities say the entire incident was captured by surveillance cameras at the home.

Police said James, a former District of Columbia firefighter, was charged in a warrant with first-degree murder. Authorities had been searching for him after they said he ran away after the shooting.

Before the shooting, Newell had asked James to help him with some yard work, and James refused, Assistant Police Chief Kevin Davis told a news conference.

As Newell stood on a stepladder outside his garage while screwing in a light bulb, James approached him from behind and shot him in the back, Davis said.

He fell to the driveway, and James stood over Newell and fired several shots, Davis said.

“It was an execution,” he said.

Police have found no motive other than the argument over yard work, Davis said.

“It’s as simple and tragic as that,” he said.

James had been living with his stepfather since he was fired from the fire department sometime in the past 18 months, said Davis, who had no details about what led to the firing.

Newell had been with the Metropolitan Police Department since 1989 and investigated dangerous assaults, MPD Assistant Chief Peter Newsham said. Newell was married and had two teenage daughters in addition to his stepchildren, Newsham said.

Online court records from Maryland show James was charged last month with violating his probation on a second-degree assault charge. He also received probation before judgment in an unrelated drunken-driving case, records show.