Deputies arrested him two days later at his Spokane apartment, according to court records. The man was booked Monday night into the Spokane County Jail on suspicion of first-degree arson and is being held on $1 million bond. On Sunday, the state investigator determined the fire was likely arson and was probably started by an open flame produced by a lighter or a match. The investigator learned the same man was also contacted by Spokane police one month earlier regarding a separate report of potential arson, according to the affidavit. Local authorities investigated the August 2025 fire at Riverside State Park, according to Washington State Patrol spokesperson Chris Loftis.