Detectives believe the "person of interest" taken into custody Saturday night in connection with the slaying of a Maryland State Trooper outside an Applebee's restaurant in Forestville is likely the man who shot the trooper.

That's based largely on the account of a person who witnessed the incident from the parking lot, a law enforcement source said Sunday.

Investigators still have unanswered questions in the killing of Trooper Wesley Brown, 24, who was working security in an off-duty capacity at the Applebee's when he was shot early Friday morning. But, for now, they consider the man they have in custody — the man in a light blue shirt who Brown escorted out of the Applebee's about 30 minutes before the shooting — to be the primary suspect, the source said.

Authorities have not publicly identified the man in custody.

"The guy that was ejected from the restaurant looks like he's probably the shooter," said one law enforcement source, speaking on the condition of anonymity because no one has been charged and the investigation is ongoing.

Officially, police said the man who was escorted from the restaurant by Brown after acting disorderly was taken into custody Saturday as a "person of interest," but he was not necessarily believed to be the shooter.

Maj. Andrew Ellis, a senior spokesman for the Prince George's County Police Department, said the shooting happened about 30 minutes after the man was escorted out, and it was possible the man could produce an alibi and clear himself of any wrongdoing. Other law enforcement sources also acknowledged that possibility and said detectives know only that the man in custody was the man escorted out.

Cpl. Clinton Copeland, another Prince George's police spokesman, said the man was being held Sunday on "an unrelated charge" that was "not related to anything dealing with this investigation." He said he did not know what that charge was or how long it might keep the man in police custody, but the investigation into Brown's killing was "moving along at a very good pace."

"They're being very careful and very cautious," Copeland said. "It's moving in a positive direction, and hopefully we will be able to close it soon."

Investigators have some evidence to indicate the man acting disorderly was also the shooter, sources have said. For one, he is the only one with a clear motive, having been escorted out of the restaurant by Brown, sources said. He was also apparently spotted by a witness in the parking lot, sources said. One law enforcement source said detectives and prosecutors are waiting to review footage from a security camera that pointed outside the Applebee's, and they are hoping to collect a few more pieces of evidence on Monday.

Law enforcement sources have said whoever shot Brown fired about a half dozen shots from a distance of 50 feet or more, and one of those rounds somehow made its way past his bullet proof vest and pierced his heart. Another round also struck Brown in the ankle, a law enforcement source said.

Brown, a 3 1/2 year veteran of the State Police who was active in the Seat Pleasant community and founded a mentoring group for youths, never had a chance to draw his weapon, police said. He was talking on his cell phone and apparently ambushed by the shooter, police said.