New York City police detectives searched a studio apartment in Las Vegas that belonged to the suspected gunman in Monday's mass shooting at a Midtown Manhattan.

Shane Tamura, 27, who fatally shot four people in the building that houses the National Football League's headquarters Monday, said in a suicide note that he had chronic traumatic encephalopathy, known at CTE,

When I look into you and dad’s eyes, all I see is disappointment,” Tamura wrote to his mother in the note. “I love you, Momma. I’m sorry.”