Authorities said they also found other links between Mr Rinderknecht and the fire on his phone, including videos that Mr Rinderknecht had taken of firefighters trying to put out the flames.
The phone also showed that he repeatedly called 911 just after midnight on New Year's day, but could not get through because of patchy mobile reception on the trailhead. There was a screen recording of him trying to call emergency services and at one point being connected with a dispatcher.
Mr Rinderknecht also asked ChatGPT: "Are you at fault if a fire is lift [sic] because of your cigarettes?"
Investigators said the suspect wanted to "preserve evidence of himself trying to assist in the suppression of the fire".
"He wanted to create evidence regarding a more innocent explanation for the cause of the fire," the indictment said.
Investigators noted that Mr Rinderknecht appeared nervous during their interview with him on 24 January this year, and his carotid artery would pulsate whenever he was asked who had started the fire.
In July 2024, five months before he allegedly set the fire, Mr Rinderknecht asked ChatGPT to create an image of a "dystopian painting" that included a burning forest and a crowd of people running away from a fire, according to investigators.
His prompt to the AI tool included the text: "In the middle [of the painting], hundreds of thousands of people in poverty are trying to get past a gigantic gate with a big dollar sign on it.
"On the other side of the gate and the entire wall is a conglomerate of the richest people.
"They are chilling, watching the world burn down, and watching the people struggle. They are laughing, enjoying themselves, and dancing."
A month before allegedly setting the fire, Mr Rinderknecht allegedly inputted a prompt to ChatGPT that included the text: "I literally burnt the Bible that I had. It felt amazing. I felt so liberated."
An outside review into the fire that was commissioned by Los Angeles County supervisors found that "outdated policies" for sending emergency alerts had delayed evacuation warnings, among other official failings.
California Governor Gavin Newsom called the arrest an important step toward "bringing closure to the thousands of Californians whose lives were upended".
He added that the state was supporting the federal investigation into the fire.