the soldier who died in the explosion wanted to serve as an “alarm signal”

Matthew Livelsberger, a 37-year-old Green Beret from Colorado Springs, Colorado, also wrote in the note that he needed to “clean [son] spirit” of the lost lives of people he knew and the “burden of lives that[il a] taken”.

Mr. Livelsberger apparently had no ill will toward President-elect Donald Trump, officials with the Las Vegas Metropolitan Police Department said.

“While this incident is more public and sensational than usual, it ultimately appears to be a tragic case of suicide involving a heavily decorated combat veteran who was battling post-stress syndrome. -traumatic and other issues,” FBI Special Agent Spencer Evans said at a news conference.

The explosion caused minor injuries to seven people, but virtually no damage to the Trump International Hotel. The authorities stressed on Friday that Mr. Livelsberger had acted alone.

“It was not a terrorist attack, it was a wake-up call. Americans only pay attention to spectacles and violence. What better way to get my message across than a gunshot with fireworks and explosives,” Mr. Livelsberger wrote in a letter found by authorities who only published extracts.

Investigators identified the driver of the Tesla — who was burned beyond recognition — as Matthew Livelsberger through a tattoo and by comparing DNA from family members. The cause of death was a self-inflicted gunshot to the head, coroner’s officials said.

Authorities extracted messages from two letters Mr. Livelsberger wrote using a cellphone notes app, Las Vegas Metropolitan Police Department Deputy Sheriff Dori Koren said.

The letters covered a range of topics, including political grievances, domestic issues and societal issues, Ms. Koren said.

Tesla engineers helped extract data from the Cybertruck for investigators, including Livelsberger’s journey from charging stations in Colorado, New Mexico and Arizona to Las Vegas, Ms. Koren said.

“We still have a large volume of data to analyze,” said the deputy sheriff. “There are thousands, if not millions, of videos, photos, documents, histories on the internet and all these things that need to be analyzed.”

A political message?

The new details came as investigators sought to determine Mr. Livelsberger’s motive, including whether he sought to send a political message with the Tesla and hotel named after the president-elect.

Tesla CEO Elon Musk recently became a member of Donald Trump’s inner circle. Neither Donald Trump nor Elon Musk were in Las Vegas early Wednesday, the day of the explosion. Both had attended Donald Trump’s New Year’s party at his South Florida estate.

Investigators have not yet explained how Mr. Livelsberger shot himself in the Cybertruck while simultaneously lighting fireworks and camping fuel packed inside, causing the explosion.

Investigators suspect Matthew Livelsberger planned a more devastating attack, but the steel-walled vehicle absorbed much of the force of the crudely constructed explosive.

Among the charred items found inside were a handgun at Mr. Livelsberger’s feet, another firearm, fireworks, a passport, a military ID card, credit cards, a iPhone and a smartwatch, said Las Vegas Metropolitan Police Sheriff Kevin McMahill. Authorities said both guns were purchased legally.

A law enforcement official said investigators learned through interviews that he may have gotten into a fight with his wife shortly before renting the Tesla in Colorado on Saturday and buying weapons. The official spoke on condition of anonymity because he was not authorized to discuss the ongoing investigation.

In recent years, Matthew Livelsberger told Alicia Arritt, a former girlfriend who had served as an Army nurse, that he suffered from significant pain and exhaustion that she attributed to head trauma.

He confided to Ms. Arritt, 39, whom he met and began dating in Colorado in 2018, about exhaustion, the pain that kept him up at night and feeling reliving the violence of her deployment to Afghanistan, Alicia Arritt said.

“My life has been personal hell for the past year,” he wrote to her in text messages during their early days of dating that she shared with the Associated Press (AP).

A highly trained man

Green Berets are highly trained special forces of the United States Army who specialize in guerrilla warfare and unconventional combat tactics.

Matthew Livelsberger has served in the Army since 2006. He rose through the ranks and was deployed twice to Afghanistan and served in Ukraine, Tajikistan, Georgia and Congo, according to the Army. He recently returned from an overseas assignment in Germany and was on approved leave when he died, according to a U.S. official.

He received five Bronze Stars, including one with a valor device for courage under fire, a Combat Infantryman Badge and an Army Commendation Medal for Valor.

Authorities searched a townhouse in Matthew Livelsberger’s hometown of Colorado Springs on Thursday as part of the investigation. Neighbors said the man who lived there had a wife and baby.

The neighbor across the street, Cindy Helwig, said she last saw him when he asked to borrow a tool to repair an SUV.

“He was a normal guy,” Ms. Helwig testified.

The truck explosion occurred hours after Shamsud-Din Bahar Jabbar, 42, plowed a truck into a crowd in New Orleans’ famous French Quarter early on New Year’s Day, killing at least least 14 people before being shot dead by police.