In a statement, the group’s news agency Amaq says the attack on Saturday night was carried out by an Islamic State fighter.
At least 53 other people were wounded in what is now known as the deadliest mass shooting in American history.
President Barack Obama has made another call for new gun laws.
Obama says the incident was a reminder of how easy it is for someone to get a hold of a weapon that could kill people.
“This massacre is therefore a further reminder of how easy it is for someone to get their hands on a weapon that lets them shoot people in a school or in a house of worship or a movie theater or in a night club. And we’ve to decide if that’s the kind of country we want to be.”
Obama has called the shooting an act of terror, saying it’s a reminder of how easy it is for someone to get hold of a weapon that could kill people.
