We're starting with an overview of a mass shooting that took place Sunday night in Las Vegas, Nevada. This is the U.S. state's most populated city. It's internationally famous for its extravagant hotels, casinos and entertainment.
And it was during an outdoor country music concert on the Las Vegas strip that gunfire was heard just after 10:00 on Sunday night. There were around 22,000 people at the show. Police say the crowd was targeted by a single gunman on the 32nd floor of a nearby hotel.
At least 58 people were killed and more than 500 others were taken to hospitals. This was the worst mass shooting in modern American history.
U.S. President Donald Trump addressed the incident on Monday morning.
DONALD TRUMP, PRESIDENT OF THE UNITED STATES: We are joined together today in sadness, shock and grief. Last night, a gunman opened fire in a large crowd, at a country music concert. It was an act of pure evil.
AZUZ: Jason Aldean, who was performing at the time of the attack, was unharmed. He described it as beyond horrific and said his thoughts and prayers went out to everyone who was there.
Support and sympathy poured in from the U.S. capital and around the world, with U.S. government leaders praising the efforts of the first responders.
Police found the suspected gunman dead inside his hotel room. They believe he killed himself. He was identified as a 64-year-old man named Stephen Paddock.
But the Las Vegas sheriff said law enforcement had no knowledge of the man and that he didn't know how this could have been prevented. He also said officials were not calling the shooting a terrorist attack at this time.
SHERIFF JOE LOMBARDO, SHERIFF OF CLARK COUNTY: Well, we have to establish what his motivation is first and there's motivating factors associated with terrorism other than distraught person just intending to cause mass casualty.
REPORTER: Is it terrorism? A much repeated question that's asked by government agencies in the wake of an attack. And while it seems simple at first, making a call can be a struggle.
UNIDENTIFIED MALE: The deadly terror attack.
UNIDENTIFIED MALE: Terror attack.
UNIDENTIFIED MALE: Terror —
UNIDENTIFIED MALE: Terror —
UNIDENTIFIED FEMALE: Terror —
REPORTER: In 2015, there were almost 15,000 acts of terror in the world. The problem is that there's no internationally recognized definition for terrorism. The U.N. has been debating it for years.
The FBI defined terrorism as the unlawful use of force or violence against persons or property, to intimidate or coerce a government, the civilian population or any segment thereof in furtherance of political or social objectives.
So, essentially, it comes down to motive. Was there a political or ideological agenda behind the attack?