Officials say the 63-year-old Debra Derrick was shot on a residential block of Lehigh Avenue around 8 p.m.
Derrick's family says she was celebrating her and her twin's birthday at the time of the shooting.
They say Derrick's twin died a few years ago after suffering from asthma.
According to family members, Derrick was about to release some balloons in her sister's honor when she heard gunfire and jumped in to protect her family.
That's when they say she was tragically shot and killed.
Derrick was rushed to University Hospital where she was pronounced dead at 8:27 p.m.
Loved ones gathered near the crime scene to comfort one another on Friday.
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Video showed several police units at the location Thursday night, which was blocked off with yellow crime scene tape.
Other people showed up injured at the hospital, and police are investigating their involvement in the incident.
No arrests were immediately made.
The Essex County Prosecutor's Office is investigating.
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