The shooting happened around 1:30 a.m. in Southwest Philadelphia along the 2000 block of South Alden Street.
Police said the suspect, who they believe is the former boyfriend, shot the current boyfriend multiple times in the chest while inside a second-floor bedroom of a house.
The 27-year-old victim died at the scene, police said.
"We're getting information that a male, a known doer, entered the property, went up to the second floor, had a verbal altercation with the victim and that's when shots were fired," said Chief Inspector Scott Small.
Shortly after that, investigators found a car that matched a description of the shooter's vehicle outside of his last known address.
Action News was there as a the Philadelphia Police Department SWAT Unit surrounded the area of South 25th and Mifflin streets in South Philadelphia.
Police blocked of all nearby intersections as they prepared to enter the home.
Investigators believed the suspect might've been inside, but later learned he was not there. The scene was cleared just before 5:30 a.m.
This marked the 26th domestic homicide in Philadelphia so far this year, authorities said.
Police say they know who the suspected shooter is, but they are still trying to track him down.