Police on Thursday arrested both suspects wanted in last month's slaying of an overnight clerk at a convenience store on the edge of Northern Liberties.

About 8 a.m., an anonymous tip led investigators to the alleged triggerman, Quasheam Richburg, 20, of North Philadelphia, who was hiding in a house on the 2000 block of Norwood Street in South Philadelphia, police said. He was arrested without incident.

By 3 p.m., Richburg's suspected accomplice in the failed robbery, Marvell Hargrove, 17, also of North Philadelphia, turned himself in at police headquarters.

Both are expected to be charged with murder, police said.

Surveillance footage captured the May 26 killing at the Trax Food Store under the Market-Frankford Line Girard Avenue Station.

Richburg shoved a sawed-off shotgun in the face of Mustafa Shaker, 50, while Hargrove tried to pry open the register, police said.

Shaker, an Egyptian immigrant who worked two jobs and had two teenage children, refused to open the register and was backing up with his hands in the air when Richburg shot him in the head, police said. The pair left with nothing, police said.

Richburg's capture marks his fourth arrest in 11 months. In each case, Richburg, wanted on a bench warrant at the time of the killing, managed to return to the streets because of reluctant witnesses and bail, court records show.

In July 2010, at a bus stop near his home, Richburg beat up and robbed a young woman who was six months pregnant with his child, according to a police report.

Richburg posted 10 percent of $4,500 bail, and the case was dismissed when the woman did not appear for three court hearings, records show. A bench warrant was issued in that case after he failed to show up for his initial court appearance. The warrant was lifted when he showed up for a later court date.

In November, Richburg was charged with robbing a man at gunpoint outside a corner store at 27th and Ridge. He could not post the 10 percent of his $50,000 bail. The victim showed up on the first listing of the case, but the defense requested a delay, which the judge granted.

The victims failed to show up for the next two court hearings, records show. Tasha Jamerson, spokeswoman for the Philadelphia District Attorney's Office, said detectives visited the alleged victim's house in an effort to bring him to court but could not find him.

Prosecutors requested more time to track down the witness, but a judge denied the request, Jamerson said. The case was dismissed and Richburg was set free in March.

On April 4, Richburg was caught fleeing police with a 9mm handgun, records show. He was charged with gun possession and his bail was set at $5,000; he posted $500 and was freed.

Richburg did not show up for a May 10 court arraignment, and another bench warrant was issued.

Less than two weeks later, Richburg shot Shaker in the face, police said.

Because Richburg's previous cases had been withdrawn, a bail commissioner may have considered them less of a factor when calculating his most recent bail, Jamerson said. She said $5,000 was not considered low for a gun charge, even with Richburg's arrests.

Contact staff writer Mike Newall at 215-854-2759 or mnewall@phillynews.com.