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An outhouse at the Muir Picnic Area that was destroyed by the Morgan Fire is photographed in Mount Diablo State Park in Danville, Calif. on Thursday, Sept. 12, 2013. Replacement and repairs will be done to areas damaged or destroyed by the fire and the many fire breaks and roads will be restored as close to their natural state as possible. (Dan Honda/Bay Area News Group)

MARTINEZ -- No criminal charges will be filed against the person whose target shooting sparked the 3,100-acre fire on Mount Diablo in September, Contra Costa County District Attorney Mark Peterson said Wednesday.

The District Attorney's Office investigation determined that there is no evidence that the unnamed person was criminally negligent when, while target shooting on his family's property off Morgan Territory Road in unincorporated Clayton, a steel projectile hit a rock and ignited dry grass.

Firefighters quickly contained the fire to a half-acre, but the wind sparked a second fire 1,000 feet away. More than 1,370 fire personnel from more than a dozen agencies battled the days-long blaze that forced the evacuation of 75 homes and a weeklong closure of Mount Diablo State Park.

"We are fully aware of the tremendous harm to property and the environment caused by the fire; however, in the final analysis, the key legal question is whether it was reasonably foreseeable that discharging a firearm in this area under these circumstances would cause a fire," Peterson wrote in a prepared statement. "Given the sheer number of times firearms have been discharged in this area and in similar areas throughout the state without causing a fire, it is the determination of this office that no criminal liability can be attached to the cause and origin of this fire."

The target shooter immediately attempted to snuff out the fire, had a family member call 911 in a timely manner, and fully cooperated with authorities, Peterson said.

"There is no evidence that the use of the involved rifle or ammunition in that area was in violation of state law. There is no evidence that this particular phenomenon had occurred before in that area, or with this particular individual," Peterson wrote. "There is little evidence that someone would know or should know that a discharged projectile would or could cause a fire in this way."

Contact Malaika Fraley at 925-234-1684. Follow her at Twitter.com/malaikafraley.