Omar Mateen, the 29-year-old shooter at Pulse nightclub in Orlando on Sunday, was born in the Queens borough of New York City.

While the FBI investigation into his motives and background continues, this is what we know so far:

• Mateen was on a terrorist watch list, based on his previous encounters with the FBI.
• Of course, there are problems with terrorist watch lists:

• Omar Mateen's wife told the FBI she tried to talk him out of his attack — but never notified law enforcement of what he was planning.
• Mateen had previously visited Pulse and had a profile on a gay dating site.
• In Florida, the mass shooting has sparked a new discussion of gun control.
• Imran Yousuf, a 24-year-old who served as a US Marine in Afghanistan, was a bouncer at Pulse Sunday morning and saved "dozens of lives" through his actions.
• Blood donations and monetary donations are still being sought.