Police are poring over what they believe are letters left by Matthew Livelsberger — the driver of the Tesla Cybertruck that exploded on New Year’s Day outside the Trump International Las Vegas Hotel — on a phone in the destroyed vehicle, authorities said Friday.

Livelsberger shared personal and political “grievances” in the recovered messages and called the attack a “wake up call,” police said.

“I know everyone is very eager to try to understand and be able to explain what happened,” Las Vegas Assistant Sheriff Dori Koren said during a press briefing on Friday. “We still have a large volume of data to go through, a lot of content to go through.”

Livelsberger, an active-duty Army soldier, 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, according to excerpts of the two letters shared by the Las Vegas Metropolitan Police Department.

The department released the two letters to the public following the press briefing.

“You’ll see that he actually calls it a stunt, in one of these documents that we’re going to release to you, that he was trying to get the attention of the American people because he was upset about a number of different things,” Sheriff Kevin McMahill of the Las Vegas Metropolitan Police Department said during Friday’s briefing when asked about the suspect’s political views. “But I’ll let those writings speak for themselves.”

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 died from a self-inflicted gunshot wound prior to the blast, the Clark County coroner confirmed Thursday evening. No one else was seriously hurt, though seven bystanders sustained minor injuries, officials said.

The evidence shows Livelsberger “thoughtfully prepared” and acted alone in the incident, Spencer Evans, special agent in charge for the FBI’s Las Vegas division, said during Friday’s press briefing. Livelsberger was not on the FBI’s radar prior to the incident, Evans said.

“Although this incident is more public and more sensational than usual, it ultimately appears to be a tragic case of suicide involving a heavily decorated combat veteran who was struggling with PTSD and other issues,” Evans said.

Authorities are also looking into a letter purportedly sent by Livelsberger and shared by the military-themed “Shawn Ryan Show” podcast on Friday. That information was sent to the FBI following the attack, Evans confirmed.

“We still have not conclusively determined that that’s from the subject, but feel confident, based on evidence that we’re uncovering on his devices, that that was, in fact, from Livelsberger,” Evans said.

In the Cybertruck, officials found credit and identification cards in Livelsberger’s name, evidence he owned the weapons found in the destroyed vehicle and identified tattoos that appeared to match Livelsberger’s body, however, severe physical injuries slowed the identification process.

The Clark County coroner ultimately identified Livelsberger — of Colorado Springs, Colorado — as the driver on Thursday. His cause of death was a self-inflicted intraoral gunshot wound.

Livelsberger was found with a gun at his feet. Two firearms — one handgun and one rifle — were found in the vehicle “burnt beyond recognition,” McMahill said.

Both weapons were purchased legally on Monday, he added.

Two phones were recovered from the vehicle, including one containing the two letters, Koren said. Investigators have been unable to access the other phone at this time, he said.

It is unclear why Livelsberger chose a Tesla or the route he took, authorities said Friday.

Livelsberger rented the Tesla vehicle on Saturday in Denver via the Turo app, before driving to Las Vegas through cities in Colorado, New Mexico and Arizona. His progress was tracked through Tesla charging stations, officials said.

The vehicle first pulled into the Trump International Las Vegas Hotel valet area just after 7:30 a.m. Wednesday, officials said. It then left the area, driving along Las Vegas Boulevard, before returning to the valet area at about 8:39 a.m., exploding 17 seconds after its arrival.

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.

The Department of Defense has turned over Livelsberger’s medical records to local law enforcement, Pentagon press secretary Sabrina Singh told reporters during a briefing on Friday.

“I just don’t have more details to share,” she added, when asked about reporting from CNN that the suspect had been diagnosed with depression last year.

Singh noted that service members are encouraged to seek help with any mental health issues.

The Las Vegas incident is not believed to have any direct connection to the New Year’s Day truck attack in New Orleans that killed 14 people — as well as the suspect — and injured 35 others, according to the FBI. The truck used in the New Orleans attack was also rented using the Turo app, officials said.

Evans reiterated Friday that there is no evidence that the two events are connected, saying there are “coincidental similarities” between them — including that both drivers were in the military, rented vehicles through the same service and stayed in an Airbnb.

There is no evidence at this time that the two drivers had any overlap even though both served in Afghanistan, Singh also said Friday.

Livelsberger was a supporter of Trump, an official briefed on the probe told ABC News. 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.

Livelsberger is believed to have told the person he rented the truck from that he was going camping at the Grand Canyon, the official told ABC News.

Investigators are still looking to determine how the items in the truck were detonated, but with the contents of the vehicle so badly burned, it may be a slow process, according to the official.

The sheriff said Musk, Tesla’s CEO, helped the investigation by having the truck unlocked after it auto-locked in the blast and by giving investigators video of the suspect at charging stations along its route from Colorado to Las Vegas.

McMahill said police believe the explosion was an “isolated incident” and that “there is no further threat to the community.”

Video played at Thursday’s Las Vegas news conference showed a load of fireworks-style mortars, gasoline cans and camping fuel canisters in the back of the truck.

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.