Shane Tamura was identified by police as the perpetrator who entered 345 Park Avenue on Monday wearing body armor and carrying a rifle. Authorities said he opened fire in the building's lobby and on the 33rd floor, killing four people, including an off-duty NYPD officer, before killing himself.Tamura, originally from California, played high school football as a running back for Granada Hills Charter. A clip from his playing days garnered attention following the incident. In the video, Tamura talked about his team’s comeback win.“We definitely had to stay disciplined,” Tamura said. “We were down 10-0, we definitely had to stay disciplined. Our coach kept saying, ‘Don’t hold your heads down, don’t hold your heads down. We tried to stay disciplined and come together as a team.”A note was found in Tamura’s pocket after the incident, referencing chronic traumatic encephalopathy, a brain condition tied to repeated head trauma in athletes. Investigators said that it was indicated in the note for his brain to be studied for signs of the disease.New York City Mayor Eric Adams said in media interviews that Tamura appeared to have blamed the NFL for his mental and physical health struggles."We have reason to believe he was focused on the NFL agency that was located in the building," Adams said on Tuesday, via MSNBC.“He appeared to have blamed the NFL for his injury,” Adams said, via CBS.Shane Tamura’s exact motives are under investigationShane Tamura relocated to Las Vegas, where he was issued a concealed firearms permit. He also briefly held a word card from the Nevada Private Investigators Licensing Board, although it expired before the time of shooting.According to police, Tamura drove cross-country from Nevada to New York, passing through Colorado, Nebraska, Iowa and New Jersey. Authorities found additional ammunition, a revolver and prescription medication inside his car."His motives are still under investigation, and we are working to understand why he targeted this particular location," New York Police Commissioner Jessica Tisch said on Tuesday, via ABC News.ABC News also reported that Tamura’s former classmate, Caleb Clarke, remembered him as a “goofball.” He added that Tamura didn't show any signs of having serious mental health issues.