A police official confirmed that the bench warrant was used to arrest the man so he could be questioned in the officer's slaying.
The man was taken into custody around 3:30 p.m. at the Bartram Village Apartments in Southwest Philadelphia, said John Patrignani, deputy chief U.S. marshal in Philadelphia.
Walker, 40, a 19-year veteran of the force, was killed Saturday morning during a robbery in North Philadelphia.
He had just completed his shift at the 22d District and was walking to a bus stop in the 2000 block of Cecil B. Moore Avenue shortly before 6 a.m. when two men stopped him.
As Walker tried to draw his off-duty gun, he was shot in the chest, the stomach, and an arm. He was pronounced dead a short time later at Hahnemann University Hospital.
Surveillance video made public this week showed Walker glancing over his shoulder toward the men, who eventually caught up to him.
In an interview with NBC10, Wayne Walker, the officer's mother, was asked her reaction to news that police were questioning a possible gunman. "I am so happy," she said. "I am so happy."
The Inquirer is withholding the name of the man because he had not been charged.
The man was on probation for illegally carrying a gun. He was convicted in 2008 and sentenced to two to four years in prison.
In February, he was arrested and charged with armed robbery. Bail was set at $500,000 and he was unable to post 10 percent, court records show. On two occasions, a witness failed to appear in court, and the District Attorney's Office withdrew the case June 12.
Walker was the fourth officer killed this year while off duty.
Officer Brian Lorenzo was killed July 8 by an alleged drunken driver while driving home from work.
Officer Marc Brady was fatally injured July 15 when struck by a car while riding his bicycle.
Officer Milan Merke died June 14, six days after his motorcycle crashed into a car that had turned suddenly in front of him. He had been on his way to an antiviolence rally.
Funeral information for Walker was announced Wednesday. Public viewings will be Sunday and Monday, Aug. 26 and 27, at Deliverance Evangelistic Church, 2001 W. Lehigh Ave.
Sunday's viewing will be from 6 to 10 p.m. Monday's viewing will begin at 7 a.m., followed by a service at 10. Burial will be in Fernwood Cemetery, Lansdowne.
A memorial fund for Walker was established Wednesday at the Police & Fire Federal Credit Union, the Fraternal Order of Police announced. Anyone wishing to donate may visit or call any PFFCU branch and ask to give to the Moses Walker Jr. Memorial Fund.
Contact Robert Moran at 215-854-5983 or firstname.lastname@example.org, or follow @RobertMoran215 on Twitter.
Inquirer staff writers Jonathan Lai and Mike Newall contributed to this article.