52-year-old Tony Martin was shot and killed in March while collecting rent from a tenant living in his West Butler Street property.
20-year-old Shaquille Henderson was later arrested and charged with the Martin's murder.
Authorities now say the weapon Henderson allegedly used was stolen from his aunt, a Philadelphia police officer in the 22nd district.
Action News has learned that an unidentified officer took the proper steps to report that her service weapon was stolen.
No further information has been released.
Philadelphia Police's Internal Affairs Department is currently investigating.