US President Barack Obama. Evan Vucci – Pool/Getty Images The US was reeling Monday after the deadliest mass shooting in American history, in which at least 50 people were killed in an attack on a gay nightclub in Orlando, Florida.

The gunman, 29-year-old Omar Saddiqui Mateen, a US citizen, reportedly pledged allegiance to the Islamic State, the terrorist group also known as ISIS, ISIL, or Daesh, during the shooting.

President Barack Obama called the massacre "an act of terror and an act of hate."

He also used the incident to reiterate his call for tighter gun control in America.

"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 a house of worship, or a movie theater, or a nightclub," Obama said. "And we have to decide if that's the kind of country that we want to be."

Obama's call came just 12 days after he addressed the issue of gun control and terrorism during a town-hall event with PBS NewsHour in Indiana on June 1.

He rejected the claims that Democrats were trying to disarm the nation, saying "more guns sold since I've been president than just about any time in US history."

"There are enough guns for every man, woman, and child in this country," he continued. "And at no point have I ever proposed confiscating guns from responsible gun owners."

Obama compared guns to cars, saying that science had been used to make driving safer but that Congress would not allow the Centers for Disease Control and Prevention to study gun violence.

"When we talked about doing effective background checks, it was resisted because the notion was we were going to take your guns away," Obama said.

He then laid out a scenario chillingly similar to the one involving the Orlando gunman:

I just came from a meeting today in the Situation Room in which I've got people who we know have been on ISIL websites, living here in the United States, US citizens, and we're allowed to put them on the "No fly" list when it comes to airlines. But because of the National Rifle Association, I cannot prohibit those people from buying a gun. This is somebody who is a known ISIL sympathizer. And if he wants to walk into a gun store or gun show right now and buy as many weapons and ammo as he can, nothing's prohibiting him from doing that, even though the FBI knows who that person is.

Mateen was investigated by the FBI twice, but the case was closed each time. He legally purchased a handgun and a long gun in the past few days before the attack, a police spokesman said in a news conference on Sunday.

Obama ended his June 1 answer with a plea: "There is a way to have common-sense gun laws … but the only way we're going to do that is if we don't have a situation which anything that is proposed is viewed as some tyrannical destruction of the Second Amendment. And that's how too often the issue gets framed."

Watch the encounter below: