According to authorities, police responded to the Sterling Apartments in the 1800 block of John F. Kennedy Boulevard at about 12:50 p.m. Tuesday.
Philadelphia Police Department Staff Inspector Sekou Kinebrew said multiple people called 911 for "shots fired" from an apartment on the 18th floor.
"I was walking downstairs to get lunch...and I got into the elevator with a police officer who seemed to be pretty rattled. She told me there was someone with a gun on the 18th floor barricaded in his apartment," said Max Detweiler, a Sterling resident.
Kinebrew said a man in his 30s shot himself following an argument with another man who left the apartment. A second bullet was shot through a window but has been accounted for.
A .40-caliber Smith & Wesson was found next to the body of the man, he said.
At about 2:15 p.m., police reopened the roads surrounding the scene. They said there was no longer a threat to the public.
Police are still looking for the man who they say left the apartment. Officers don't believe he did anything against the law, but said they would like to hear from him.