During a press briefing on Monday morning, President Donald Trump called the Las Vegas mass shooting--the deadliest in US history--an "act of Pure Evil."

A gunman opened fire from a casino balcony into a crowd at a Las Vegas country music festival Sunday night killing at least 58 people and injuring 500 others.

Trump said the FBI, Homeland Security, and local authorities are working on this investigation and will provide updates when available.The president continued to thank the Las Vegas metro police department and first responders.

"The speed in which they acted was miraculous and saved more lives," said Trump [VIDEO] during the press briefing.

The president said he will be visiting the families and first responders in Las Vegas on Wednesday. Trump also said flags will be flown at half-staff today.

The massacre

Las Vegas Metro Police have identified the gunman as Stephen Paddock--a 64-year-old with at least 10 rifles in his arsenal. Paddock shot from a 32nd-floor balcony in the nearby Mandalay Bay Casino into a crowd of 22,000 attending a Jason Aldean concert.

Thousands of concert-goers ran into the streets seeking shelter and aid. The shooting allegedly lasted about 10 minutes.

The sheriff said Paddock had no prior criminal history. Police announced there is no connection to international terrorism. Paddock's motive is allegedly still unclear at this time.

The New York Times is reporting a SWAT unit quickly swarmed Paddock's room.

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Police believe Paddock had killed himself before the unit entered.

The Mesquite Police Department was granted a search warrant and entered Paddock's home in Mesquite, Nevada. They found ammunition, but nothing out of the ordinary according to CNN.

The victims

According to the New York Times, Sherriff Joseph Lombardo of the Las Vegas Metropolitan Police Department said on Monday morning the injuries from this shooting could be well over 400 people. Of those fatally shot, one of them was an off-duty Las Vegas police officer.

Lindsay Padgett, 29 and attendee of the concert, told ABC News she originally thought the "popping sounds" were a part of Aldean's show. Then she saw people around her being shot or seeking shelter on the ground. She said when attendees began to run they did not stop until they entered a nearby airplane hangar.

None of Padgett's friends or family were injured, but she said she was sure they were all going to die.