The brother of the gunman in the Las Vegas mass shooting says he was "completely dumbfounded" after learning of the attack, which left more than 50 dead and 400 injured during a country music festival. 

Eric Paddock, who lives in Orlando, Florida, told the Orlando Sentinel he has spoken with police about the shooting and his brother, Stephen Paddock. 

"We are completely dumbfounded," he told the newspaper. "We can’t understand what happened."

Through tears, Eric Paddock also talked with the Las Vegas Review-Journal, saying he never thought his brother was capable of this violence.

"There is no reason we can imagine why Stephen would do something like this," Paddock told the newspaper. "All we can do is send our condolences to the people who died. Just no reason, no warning."

Eric Paddock said the last time he spoke to his brother was after Hurricane Irma last month. "It’s like an asteroid just fell on top of our family," he said. 

Stephen Paddock opened fire from a high floor of the Mandalay Bay casino while singer Jason Aldean was performing as part of the three-day Route 91 Harvest country music festival on the Las Vegas Strip, police said. 

Authorities say Stephen Paddock committed suicide before police made contact with him. He was found dead on the 32nd floor of the casino. 

Police have not released a motive for the attack and did not immediately call the shooting a terrorism incident. Las Vegas Metropolitan Sheriff Joseph Lombardo said Stephen Paddock did not leave behind any notes or indications as to why he attacked the concertgoers.

"We have to establish what his motivation is first," Lombardo said when responding to a question about why the shooting hasn't been labeled a terrorism incident. "There are motivating factors associated with terrorism other than a distraught person just intending to cause mass casualty. Before we label with that, it will be a matter of process."

Lombardo said Paddock had 10 rifles and had been staying in his room since Thursday.

Paddock was using the ID of Marilou Danley, his roommate, whom police at first were calling a person of interest in the investigation. But Lombardo said that police had located Danley outside the United States and that she was not thought to have been involved in the attack.