(LAS VEGAS) -- Matthew Livelsberger used ChatGPT to help plot the Tesla Cybertruck explosion outside the Trump International Hotel Las Vegas on New Year's Day, authorities revealed on Tuesday.
Police have "clear evidence" that Livelsberger used the generative artificial intelligence tool to "help plan his attack," Sheriff Kevin McMahill of the Las Vegas Metropolitan Police Department told reporters during a press briefing on Tuesday.
Livelsberger, an active-duty Army soldier who authorities said died by suicide in the incident, asked questions about explosives and what would set off certain types of explosives, police said.
McMahill said he believes this is the first case on U.S. soil in which ChatGPT/AI helped a suspect build a device, calling it a "concerning moment" and a "game changer." He added it is also "instructive" for other law enforcement agencies and is releasing information where they can in the case.
A spokesperson for OpenAI, the developer of ChatGPT, said the company is "saddened by this incident and committed to seeing AI tools used responsibly."
"Our models are designed to refuse harmful instructions and minimize harmful content," the spokesperson said in a statement to ABC News. "In this case, ChatGPT responded with information already publicly available on the internet and provided warnings against harmful or illegal activities."
"We're working with law enforcement to support their investigation," the spokesperson added.
Through ChatGPT, the suspect looked at "trying to figure out the amount of explosives needed in order to conduct the explosion he was looking to cause," Las Vegas Assistant Sheriff Dori Koren said during the press briefing.
He also used it to try to figure out where to buy fireworks, how much and how they compare to other explosive materials, Koren said. An "important component" of his inquiries involved the velocity of the bullet fired from the firearm and "determining whether that would ignite the explosives," Koren said.
Livelsberger, of Colorado Springs, Colorado, died from a self-inflicted gunshot wound just prior to the blast, according to the Clark County coroner. Two firearms -- one handgun and one rifle -- were found in the vehicle, police said.
The Cybertruck had over 60 pounds of pyrotechnics, and 20 gallons of fuel were poured over the fireworks and explosive material in the back of the truck, according to Kenny Cooper, assistant special agent in charge of the Bureau of Alcohol, Tobacco, Firearms and Explosives' San Francisco field division.
Investigators believe the muzzle flash alone could have been an ignition source for the fuel-air explosion, though several other possible sources have not been ruled out, he said.
Police said Tuesday they have also recovered a six-page document on a phone found in the Cybertruck that showed a "variance of grievances and a constant evolution of his plans or intents of what he wanted to do," Koren said.
In the document, the suspect was critical of the Biden administration and talked about having graphic memories of his time in battle and losing his teammates, according to Koren. He also mentioned being "super high on weed and drinking," which investigators are still working to confirm, Koren said. The document also showed his mental health struggles, which "builds upon that potential PTSD that we're referring to," Koren said.
"He does transition at some point, and talks about being concerned of the media labeling them as a terrorist and that he had no intent on killing anyone else besides from himself," Koren said.
Livelsberger's writings indicate he had considered planning to set off the explosion at the glass walkway at the Grand Canyon but changed his mind, for whatever reason, to the Trump Hotel, police said.
"He does talk about his intent to make this as public as possible," Koren said.
Police believe parts of the document may be classified and are working with the Department of Defense to understand if it can all be released.
The Las Vegas Metropolitan Police Department last week released two additional letters found on a cellphone retrieved from the Cybertruck. In the letters, Livelsberger said the country was being led by the "weak" and those out to "enrich themselves," while also claiming the incident was not meant as a terrorist attack but a "wake-up call."
In one of the letters police say were found on his phone, Livelsberger expressed support for Donald Trump and the president-elect's allies, Elon Musk and Robert F. Kennedy Jr. He also expressed disdain for diversity, equity and inclusion initiatives and income inequality and expressed a concern about homelessness, according to the letters.
Livelsberger also sent an email shared by the military-themed "Shawn Ryan Show" podcast on Friday, authorities confirmed on Tuesday. That information was sent to the FBI following the attack, federal officials said.
The evidence shows Livelsberger "thoughtfully prepared" and acted alone in the incident, federal authorities said. He was not on the FBI's radar prior to the attack, authorities said.
No one else was seriously hurt, though seven bystanders sustained minor injuries, officials said.
Livelsberger served as a Green Beret in the Army and was on approved leave from serving in Germany at the time of his death, a U.S. Army spokesperson said Thursday.
He received extensive decorations in combat, including the Bronze Star with a "V" device for valor, indicating heroism under fire. Livelsberger received four more standard Bronze Star medals, according to Army records. He also earned the Afghanistan Campaign Medal with three stars. Each star represents service in a separate campaign in Afghanistan.
Livelsberger had been receiving mental health assistance over the last year, a U.S. official confirmed Friday.
Another U.S. official confirmed that officials thought Livelsberger was stable enough to go home for Christmas and his leave was approved.
His wife, who investigators spoke to in Colorado Springs, said he had been out of the house since around Christmas after a dispute over allegations of infidelity, the official said.
His wife told officials she did not believe Livelsberger would want to hurt anyone, the official told ABC News.
If you are struggling with thoughts of suicide or worried about a friend or loved one, call or text the Suicide & Crisis Lifeline at 988 for free, confidential emotional support 24 hours a day, seven days a week.
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