It happened around 8:30 p.m near the intersection of 29th Street and Girard Avenue.
Fire officials say upon arrival at the scene, Devin Gold, 27, was found dead inside the first floor of the apartment. According to police, Gold was stabbed multiple times.
Firefighters also found a 40-year-old man on the first floor. Police say the man was trying to cut his wrists. He was rushed to an area hospital where he's listed in critical condition.
Investigators have not said who stabbed Gold.
"Firefighters found indications that this may be a possible crime scene and at this point, we're treating it as a crime scene," said Assistant Fire Chief Harry Bannon.
Officials say two other people in a second-floor apartment managed to escape the blaze unharmed through the rear of the property.
The cause of the fire is still under investigation.
Anyone with any information is asked to call police at 215-686-TIPS.