It happened just before 6 p.m. on the 5000 block of Summerdale Avenue when police say a 12-year-old boy found the illegal device in a trash can.
"Just know up front you are playing with death," said Philadelphia Police Captain Sekou Kinebrew, talking about M-80s, homemade firecrackers.
The explosion left the boy's hands partially amputated.
"He has injuries to both of his hands. We believe he lost a finger to one hand and he has severe injuries to the knuckles and palm of his other hand," said Chief Inspector Scott Small with the Philadelphia Police Department.
Small says the boy was at a rec center basketball court when the incident occurred.
"It appears that the child attempted to light the device, didn't realize that he actually lit it. And then he picked it back up, not realizing that enough heat had gotten on the other side of the tubing. It was enough to cause a flash powder to become volatile and explode," said Kinebrew.
Police say the illegal device was equivalent to a quarter-stick of dynamite.
Jamia Bradley was in the park at the time of the explosion.
"It was a very loud noise. It was a very loud dynamite," she said. "The boy flew in the air."
Immediately after the explosion, the boy ran from the park across the street to a beer distributor for help.
Tena Burgess was returning home from work when she saw the scene.
"People were all around him. The ambulance was pulling up, the cops were around him. It was horrible," she said
This incident comes just a week after a 9-year-old girl suffered "life-altering injuries" after an illegal explosive device exploded inside her Kensington home.
These are not fireworks. They are illegal, dangerous, explosive devices that could cause you to lose a limb or your life. If you see them (or people selling them) call 911 immediately. pic.twitter.com/3X1htsKbmD— Philadelphia Police (@PhillyPolice) July 9, 2019
Small says both incidents may be connected due to the illegal nature of the explosive device.
"These are illegal devices. There are not commercial and they are not meant for commercial," Small added.