At least 20 people have been killed and at least 42 injured after a shooting at a gay nightclub in Orlando, Florida, police say.
Orlando Police said officers entered the Pulse Club about three hours after the shooting unfolded - and killed the attacker, who had taken hostages.
They called it an act of terrorism, but said they did not yet know if it was domestic or international.
Relatives have been gathering at local hospitals desperate for news.
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Image copyright Orlando Police Image copyright Orlando PoliceA man who had been inside the club earlier described a situation of chaos outside as the number of casualties became apparent.
"There were just bodies everywhere," Christopher Hansen said. "In the parking lot, they were tagging them - red, yellow - so they knew who to help first and who not help first. Pants down, shirts cut off, they had to find the bullets. Just blood everywhere."
Footage from the scene showed dozens of emergency vehicles at the scene and people being treated on the pavements.
Some of the injured were reportedly brought to the Orlando Regional Medical Center in police pick-ups.
One woman said she had received a text message and phone call from her daughter inside the club, who said she had been shot in the arm.
Some witnesses said they heard as many as 40-50 gunshots as the incident unfolded.
Image copyright EPA Image copyright Orlando PoliceMore than 100 people were reported to have been enjoying a Latin-themed night in the club, which calls itself the hottest gay bar in the city, when the attack began.
Ricardo Negron Almodovar told BBC News that the shooter opened fire at around 02:00 local time (06:00 GMT), as the club night was coming to a close.
"We heard rapid fire go off. In the room I was in, people went down to the floor. I wasn't able to see the shooter or people get hurt.
"At some point, there was a brief pause, and a group of us got up and went to the exit that leads to the patio area outside. We found an exit and after that... I just ran."
Another man, Anthony Torres, said he heard people screaming that others in the nightclub were dead.
Image copyright FacebookAccording to the Mass Shooting Tracker, there were 372 mass shootings - defined as a single incident that kills or injures four or more people - in the US in 2015. Some 475 people were killed and 1,870 wounded.
The latest incident comes as Orlando is still reeling from the fatal shooting on Friday night of 22-year-old singer Christina Grimmie following a concert in the city.
She had been signing autographs when she was shot by 26-year-old Kevin James Loibl, who then killed himself. It is not clear what Loibl's motive was.
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