The 27-year-old man who shot and killed four people at a Midtown office building on Monday carried a note in his pocket, police sources told ABC News.

The gunman, Shane Tamura, opened fire in a Manhattan building housing NFL offices, later committing suicide, with indications he may have had CTE.

The shooter who killed four including Blackstone executive and NYPD officer left suicide note indicating he believed he had CTE from brain trauma, Adams says

Wearing body armor and wielding an assault-style rifle, the alleged gunman burst into a Midtown Manhattan office building shooting victims at random.

Shane Devon Tamura, 27, identified by the NYPD as the Midtown Manhattan office building shooter/Obtained by ABC News(NEW YORK) -- The man who opened fire in a Midtown Manhattan office building, killin

New York Police Department has not officially stated the motive of Shane Tamura shooting an NYPD official and other civilians dead in the Manhattan Midtown skyscraper.

The office building, located at 345 Park Avenue, houses some of the country’s top financial firms and the National Football League. According to the company's website, Blackstone stands as the world’s largest alternative asset manager, managing over $1 trillion in assets under management.

Flags across New York are flying at half-staff to honor the victims of Monday’s deadly Midtown Manhattan office shooting, including an NYPD officer.

The alleged gunman at a shooting rampage in a Midtown Manhattan office building was identified as 27-year-old Shane Tamura, of Nevada.