The attack took place at the Bellingham Retirement Community in West Chester at around 6.30pm local time.
The area has been shut off as police continue to search for the gunman, who is believed to have fled.
Police have implemented a two-mile radius lockdown surrounding the retirement community.
West Chester Area School District issued an alert, stating they had locked down schools in the area.
Investigators also believe the gunman may be driving a van, according to ABC6.
Reports also indicate the suspect may also be responsible for a shooting which took place in a property in the Greater Downingtown Area.
Mike Galczyk, whose daughter works in the retirement home, said: “She said ‘We’re on lockdown.’ At first I thought she was kidding.
“She’s texting us saying she’s hiding inside with her team.
“She told us to stay safe out here.”
More to follow…