Facebook has set up a crisis response page so people who are in Las Vegas can let people know they are safe.
More than 50 people died in the shooting and at least 400 people have been injured in the shooting, according to Las Vegas police. The shooting started around 10:08 p.m. local time.
Those numbers would make this the deadliest mass shooting in United States history.
The suspect has been identified as local man Stephen Paddock, 64. Paddock was shooting from the 32nd floor of the Mandalay Bay, Sheriff Joe Lombardo said. Lombardo said the shooter is dead. Police believe Paddock killed himself before law enforcement entered the room, Lombardo said.
People can check in to let Facebook friends now they are in Las Vegas and that they are safe.
Police also advise people to call 1-866-535-5654 to check in on loved ones.