The largest wildfire in California history was caused by a claw hammer, according to the state's fire protection agency.

Cal Fire said Thursday that the Ranch Fire, which first sparked last July, began when a Potter Valley property owner was hammering a metal stake into the ground, The Fresno Bee reports.

Cal Fire’s deputy director, Michael Mohler, told the Bee that incident was a “complete accident.”

The person wasn’t identified, and no charges will be filed, the Bee reports.

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The person was reportedly trying to install a shade barrier, but the hammering lit up vegetation on the nearby ground. Combined with strong winds and dry conditions that day, the fire quickly became too large to tame.

The Ranch Fire, one of the two fires making up the Mendocino Complex fires, torched 410,203 acres. A firefighter was killed, three people were injured and 280 buildings were burned as a result of the flames.