A former college professor has been charged with starting four wildfires in northern California.
It is alleged that Gary Stephen Maynard, 47, ignited blazes in July and August which could have trapped crews as they fought the Dixie Fire – the second-biggest wildfire in state history.
More than 6,000 firefighters battled the flames, which destroyed more than 1,000 homes, businesses and other structures.
Maynard is accused of setting the Cascade and Everitt fires, on 20 and 21 July, and the Ranch and Conard Fires on 7 August.
Investigators followed Maynard’s black Kia Soul car as they pursued their inquiries.
Agents with the US Forest Service started investigating him after the Cascade Fire was reported on the western slopes of Mount Shasta.
According to court papers, Maynard was found under the car, its front wheels stuck in a ditch and its undercarriage on a boulder.
When a second fire erupted on Mount Shasta the following day, investigators apparently found tyre tracks similar to those made by the Kia.
After Maynard was stopped briefly by police on 3 August, a tracker was placed under his car.
His movements were then followed for hundreds of miles. Investigators said he travelled to the area where the Ranch and Conard Fires erupted in the Lassen National Forest.
“It appeared that Maynard was in the midst of an arson-setting spree,” court papers said.
He faces up to 20 years in prison and a $250,000 (£186,000) fine for each count of arson to federal property, the US Attorney’s Office for the Eastern District of California said in a statement.
He has denied setting the blazes, court papers added, and is in custody pending trial.
In August, assistant US attorney Michael Anderson wrote in a detention memo that Maynard had entered the evacuation zone and “began setting fires behind the first responders fighting the Dixie Fire”.
This “increased the danger to the first responders”, Mr Anderson added.
Maynard appears to have taught briefly at Santa Clara University and Sonoma State University, where a Gary Maynard was listed as a lecturer in criminal justice studies specialising in criminal justice, cults and deviant behaviour.
He is no longer with either institution.