Twelve years after moving to the United States from Bangladesh, Didarul Islam sought to join the ranks of the nation's largest police department because he "got inspired" by the "blanket" of protection the NYPD provided to his community, according to an essay he wrote as part of his police academy application.

Investigators are examining why the gunman who killed four people before taking his own life at a New York City office tower targeted the National Football League and whether he suffered from a brain disease.

The New York City office building where a gunman fatally shot four people and himself reopened Monday, one week after the deadly rampage.Workers returned to 345 Park Ave., in Midtown Manhattan under the watchful eyes of NYPD officers and a surplus of additional security following the mass shooting.