LAS VEGAS (KLAS/AP) -- “This was not a terrorist attack, it was a wake up call,” said a note found on a phone inside the Tesla Cybertruck that exploded on New Year’s Day outside the Las Vegas International Trump Hotel, according to police.   At a news conference Friday, law enforcement officials gave additional details on the events that led up to Matthew Livelsberger, 37, driving a Tesla Cybertruck to the hotel and detonating explosive materials inside it. Livelsberger died from a gunshot wound to the head just before the explosion, the coroner’s office ruled Thursday. Sheriff Kevin McMahill said Livelsberger was positively identified by a number of things, including tattoo comparisons, showing a tiger arm tattoo on a photo of Livelsberger that matched one found on his body.  Video from public areas, call data records, financial records, and Tesla charging station records were used to determine the route Livelsberger took as well as determine that he was the only person in the Cybertruck. “It’s evident that [Livelsberger] considered, planned, and thoughtfully prepared for this act alone,” FBI Special Agent Spencer Evans said. Evans added that despite the public nature of the incident, it “ultimately appears to be a tragic case of suicide involving a heavily decorated combat veteran who was suffering with PTSD and other issues.” The suspect apparently harbored no ill will toward President-elect Donald Trump, Clark County sheriff’s officials said. Livelsberger wrote in the note that he needed to “cleanse my mind” of the lives lost of people he knew and “the burden of the lives I took,” Livelsberger added. Authorities say there are still questions about why he chose that car and location. “It’s not lost on us that it’s in front of the Trump building, that it’s a Tesla vehicle, but we don’t have information at this point that definitively tells us or suggests it was because of this particular ideology,” Spencer Evans, the Las Vegas FBI’s special agent in charge, said Thursday. “This was not a terrorist attack, it was a wakeup 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 a letter found by authorities who released only excerpts of it. Police shared another excerpt from the first letter: “Fellow servicemembers, Veterans, and all Americans. TIME TO WAKE UP! We are being led by weak and feckless leadership who only serve to enrich themselves.” Asked Friday about whether Livelsberger had been struggling with any mental health issues that may have prompted his suicide, Pentagon spokeswoman Sabrina Singh told reporters that “the department has turned over all medical records to local law enforcement.” A law enforcement official said investigators learned through interviews that he may have gotten into a fight with his wife about relationship issues shortly before he rented the Tesla on Saturday and bought the guns. The official spoke on the condition of anonymity because they were not authorized to discuss the ongoing investigation. The suspect confided to a former girlfriend — who had served as an Army nurse — that he faced significant pain and exhaustion that she says were key symptoms of traumatic brain injury. Livelsberger was a five-time Bronze Star recipient, including one with a V device for valor under fire. He was very private but shared images and texts with Alicia Arritt, 39, who he met and began dating in Colorado in 2018. In them he opened up about exhaustion, pain that kept him awake at night and reliving violence from his deployment in Afghanistan. “My life has been a personal hell for the last year,” said Arritt during the early days of their dating, according to text messages she provided to the AP. “It’s refreshing to have such a nice person come along.” Arritt also served on active duty in the Army as a nurse from 2003 to 2007, deploying to the military’s massive medical complex in Germany where she helped treat many soldiers with traumatic brain injuries and blast injuries from intense ground combat in Afghanistan and Iraq. She said the military failed to get Livelsberger the care he needed, symptoms she saw in him as early as 2018. “He would go through periods of withdrawal, and he struggled with depression and memory loss,” Arritt said. “He said it was a blast injury. He got several concussions from that.” Livelsberger also had a hard time with post-traumatic stress disorder and would relive some of the violence and killings he had a role in or witnessed in Afghanistan. “I would encourage him to get therapy, and he would give me reasons that he couldn’t,” Arritt said. “There was a lot of stigma in his unit, they were, you know, big, strong, Special Forces guys there, there was no weakness allowed and mental health is weakness is what they saw.” The Associated Press contributed to this report.