This is the first picture of a gunman who killed 50 people after storming into a gay nightclub in Florida.
Omar Mateen stormed into the Pulse Club in Orlando, Florida, at about 2am local time today.
He then began shooting at the crowd, killing about 50 people and injuring 53.
Mateen was 29 and was a US citizen who lived in Port St. Lucie.
It is believed he was not on a terrorism watchlist. Police have been investigating possible links to Islamist extremism.
However, it is thought he was being investigated over an unrelated crime.
It has emerged that Twitter accounts linked to ISIS have been celebrating the attack.