Law enforcement officials are investigating whether Las Vegas gunman Stephen Paddock had been planning an earlier attack in the city, a law enforcement source confirmed to CBS News' Pat Milton.

Paddock, 64, opened fire from the 32nd floor of the Mandalay Bay hotel in Las Vegas late Sunday, killing 58 and wounding more than 500 others at the Route 91 music festival on the Strip below. According to a law enforcement source, investigators are looking at whether he may have first had his sights on the "Life is Beautiful" festival on Sept. 22 to Sept. 24.

The source, who was briefed on the police investigation, said Paddock had apparently tried to get a room at The Ogden and another hotel in downtown Las Vegas, but apparently the specific suites he requested were booked. The source speculated that Paddock may have been seeking rooms that were strategically located to the festival to launch an attack.

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The Daily Beast first reported that Paddock may have been planning an earlier attack.

Paddock's motive for the deadly massacre remains unclear. His brother, Eric Paddock, said at a press conference Tuesday that the shooting was not representative of the "Steve we know, we knew."

"If you are going to call him crazy cause he's angry, then better call everyone on the news crazy person," Eric Paddock said.

Ahead of the shooting, Stephen Paddock transferred more than $10,000 to a bank account in the Philippines, a law enforcement source told CBS News. Authorities believe his girlfriend, Marilou Danley, had traveled there before the shooting occurred. They say they have many questions for her when she returns to the U.S.