A baby delivered after his mother was killed by gunfire intended for someone else has also died.
Megan Doto, 26, was sitting outside her home in the Frankford neighbourhood of Philadelphia when she was struck in the face by a stray bullet.
Homicide Captain James Clark said a man dressed in black fired more than 10 shots at a white vehicle that was a block away from where Ms Doto was located.
After the shooting, just before 11am on Sunday, Ms Doto was rushed to Temple University Hospital but was pronounced dead less than two hours later.
Doctors were able to deliver the baby, which had been due on October 15, by emergency Caesarean section, but hospital spokesman Chris Guadagnino said early on Monday that the child had died.
Before she was killed, Ms Doto posted on her Facebook page that she planned to call the boy Carmine Joseph.
Investigators are trying to determine the circumstances of the shooting, and a $40,000 (24,600) reward is being offered for information leading to an arrest.
Philadelphia Police Commissioner Charles Ramsey expressed outrage over the young woman’s killing.
“These guys don’t care about daylight, they don’t care about it being a Sunday, they don’t care how beautiful the weather,” he told local radio station KYW.
“They’re just evil thugs and they will do whatever, whenever they can.”
Neighbours told local media that Ms Doto often sat outside her home in Adams Avenue reading and was excited about her new baby.
Ms Doto was reportedly looking after a neighbour’s seven-year-old daughter when she was shot. The child was unhurt.