A highly decorated army soldier who fatally shot himself in a Tesla Cybertruck just before it blew up outside the Trump hotel in Las Vegas left notes saying the New Year’s Day explosion was a stunt to serve as a “wake-up call” for the country’s ills, investigators said on Friday.

Matthew Livelsberger, a 37-year-old Green Beret from Colorado Springs also wrote in notes he left on his cellphone that he needed to “cleanse” his mind “of the brothers I’ve lost and relieve myself of the burden of the lives I took”. Livelsberger served in the army since 2006 and deployed twice to Afghanistan.

“This 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 point across than a stunt with fireworks and explosives,” Livelsberger wrote in one letter found by authorities and released Friday.

The explosion caused minor injuries to seven people but virtually no damage to the Trump International Hotel. Authorities said that Livelsberger acted alone.

Livelsberger’s letters covered a range of topics including political grievances, societal problems and both domestic and international issues, including the war in Ukraine. He said in one letter that the US was “terminally ill and headed towards collapse”.

Tesla engineers, meanwhile, helped extract data from the Cybertruck for investigators, including Livelsberger’s path between charging stations from Colorado through New Mexico and Arizona and on to Las Vegas, according to Assistant Sheriff Dori Koren.

“We still have a large volume of data to go through,” Koren said on Friday. “There’s thousands if not millions of videos and photos and documents and web history and all of those things that need to be analysed.”