• Manhattan mass shooting: A lone gunman killed four people, including a New York Police Department officer, in Midtown before killing himself. The shooting happened during rush hour on Monday evening at a Park Avenue skyscraper that includes corporate offices for the National Football League.

• The shooter: The gunman was identified as 27-year-old Shane Devon Tamura from Las Vegas. He had a suicide note in his pocket expressing grievances with the NFL and saying he suffered from CTE, a disease linked to head trauma, according to a source. In the note, he also asked for his brain to be studied.

• The victims: The officer killed, Didarul Islam, was a 36-year-old immigrant from Bangladesh. He had two young sons and his wife is pregnant with their third child. Another person who was shot survived and is in critical but stable condition. An NFL employee was seriously injured, according to a staff memo.

The gunman who shot five people, killing four, in Midtown Manhattan on Monday was a former competitive football player who expressed grievances with the National Football League, whose corporate offices are in the building that was attacked.

Here’s what we know about the shooter: