A native of St. Louis, Martin moved to Philadelphia in the 1980s to train as a boxer. He retired with a 34-6-1 record, with 12 knockouts. He lost his last fight by decision to Julio Cesar Chavez in 1997.
"Boxing was his love," said Peete, 40, who flew from St. Louis after she learned of the homicide.
Martin was shot several times on the third floor of the rental property in the 1300 block of West Butler Street about 2 p.m., according to police. He was pronounced dead at the scene. No arrests had been reported as of Monday evening.
Martin, a married father of four adult children and the grandfather of seven, was at the property to collect rent when he was gunned down, according to Peete.
"He didn't have any issues with any of his tenants," Peete said. "I don't know what happened. All I can say is, something happened and he was shot."
A tenant said he had no comment Monday. The property still had remnants of police tape.
Martin had worked for the U.S. Postal Service since the 1980s. The agency confirmed Monday that Martin was employed as a mail-processing clerk at the Philadelphia Processing and Distribution Center in Eastwick. Martin's coworkers said he was well liked, according to Postal Service spokeswoman Cathy Yarosky.
Martin had had a license to rent the Butler Street property since 2006, according to Maura Kennedy of the Department of Licenses and Inspections. She said L&I had no open violations concerning the property and no complaints from neighbors since 2009.
A Butler Street neighbor said Martin was a "decent person."
Family members were grieving at Martin's main residence in East Germantown.
"Our family will not rest or sleep until the police apprehend this person," Peete said. "I would ask they turn themselves in."
Contact Sulaiman Abdur-Rahman at firstname.lastname@example.org or follow on Twitter @sabdurr.
Inquirer staff writer Matt Breen contributed to this article.