Concord police received a report of shots fired in the area of Adelaide and Laguna streets at 4:48 a.m.
As officers were responding to the call, a second person called police to report that someone had just dumped what looked like a gun into some bushes in the area.
Other witnesses told officers at the scene that they saw two people running through backyards and jumping over fences in the 1500 block of Adelaide Street, Cerletti said.
As officers were setting up a perimeter, they received another call from Martinez police reporting that they had just stopped a car in Martinez and found a person inside who said he had been shot in Concord.
Meanwhile, in the area of Detroit Avenue, officers spotted somebody jumping over a fence. They ordered the person to stop, but he allegedly kept running and police released a canine, Cerletti said.
The dog bit the suspect, later identified as 22-year-old Concord resident Armando Rugen, and he stopped.
While they were arresting Rugen, the officers heard a second person still jumping fences in the area. They followed the sounds and arrested the person fleeing, a 17-year-old Concord boy.
Officers then went to the area where the person had reported seeing someone ditch a gun and found a shotgun, Cerletti said.
Doctors at Contra Costa Regional Medical Center in Martinez told police the victim appeared to have been shot in the face and head with a shotgun, Cerletti said.