U.S. Marshals and Philadelphia police have arrested a man sought as the triggerman in the May 26 fatal shooting of an overnight clerk at a convenience store under the Market-Frankford Lines' Girard Avenue station, officials say.

Acting on a tip, lawmen found Quasheam Richburg, 20, at a residence on the 2000 block of South Norwood Street in South Philadelphia about 8:30 a.m., officials said.

He was taken into custody without incident, officials said.

Richburg had been sought in the shotgun killing of Mustafa Shaker, a 50-year-old Egyptian immigrant, during a stickup at the Trax Foods store on Front Street.

Shaker, an Egyptian immigrant who worked two jobs and had two teenage children, was backing up with his hands in the air when he was shot, police said.

The capture marks the fourth time Richburg, of the 2500 block of Ridge Ave., has been arrested in the last 11 months. In each case, Richburg, who was wanted on a bench warrant at the time of the murder, managed to slip out of jail due to reluctant witnesses and low bails, court records show.

In July 2010, Richburg beat up and robbed his six-month pregnant girlfriend, police reports say. Richburg posted $460 bail and the case was dismissed when the woman did not appear for three court hearings. A bench warrant also was issued for Richburg 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 2010, Richburg robbed a man at gunpoint outside a corner store at 27th and Ridge in North Philadelphia. Richburg could not post the $50,000 bail. The victim showed up for court on the first listing of the case, but the defense requested a delay, which a judge granted. When the victim did not show up for two hearings months later the case was dismissed and Richburg was set free this past March.

Just three weeks later, in April, Richburg was caught fleeing police with a 9mm handgun. Despite his arrest record and bench warrant history, the repeat offender was granted $5,000 bail, of which he posted $500, and was again set free. He did not show up for his May 10 court hearing. Just 12 days later, Richburg shot Shaker in the face, police said.

Police are still searching for Marvell Hargrove, 17, of North Philadelphia, who they say assisted Richburg in the robbery.

A reward of $1,500 was posted today for information leading to his capture.

Surveillance footage from the store shows Hargrove struggling to open the register, while Richburg shoved the barrel of the shotgun in Shaker's face, police said.

Tipsters are being asked to call the homicide unit at 215.686.3334

Contact staff writer Mike Newall at 215.854.2759 or mnewall@phillynews.com.