According to police, four people, all armed with semi-automatic handguns, fired more than 100 shots at a crowd of people at about 10:30 p.m. Sunday.
Witnesses said, at first, they mistook the gunshots at 60th and Sansom streets for fireworks. Then they started to run.
After the shooting, the suspects are seen getting into a dark grey sedan, possibly a Nissan, with tinted windows. The car headed westbound on Walnut Street toward 61st Street.
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One of the victims has been identified as 23-year-old Sircarr Johnson Jr., the owner of Premiere Bande, a clothing store in West Philadelphia.
Johnson had invited the community to an Independence Day barbecue, which was also an anniversary party for his store.
Salahaldin Mahmoud, 21, and a friend of Johnson's, was also shot and pronounced dead at the scene.
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According to police, a 16-year-old girl and a 36-year-old woman sustained non-life-threatening injuries during the shooting.
Anyone with information about the suspects or the shooting is asked to call police.
A $20,000 reward is being offered for information leading to an arrest and conviction in this case.