An 18-year-old man walking in the area suffered wounds to his back when shrapnel blew through the walls and roof of the portable toilet around 10:40 p.m. He was taken to Santa Rosa Memorial Hospital and was in stable condition Monday.
Sgt. Andrew Urton said the suspect admitted he learned how to make the pipe bomb on the Internet and bought the materials from a local store.
The teen assembled the bomb at his east Petaluma home and went to the park alone on the Fourth of July to detonate it, Urton said.
He ran away when he heard the injured man scream, Urton said. Lt. Tim Lyons said a witness recognized the teen and contacted police Saturday night.
The boy was arrested around 7 p.m. Monday at his home and booked into juvenile hall for explosion of a destructive device causing great bodily injury, Lyons said.
The pipe bomb was a 6-inch metal pipe with explosive material inside, Lyons said. The cap of the pipe blew off and became embedded in the victim's back, Lyons said.
Fortunately the man did not suffer any spine injuries, Lyons said.