“We are praying for the wounded, the victims and the families hit by this terrible tragedy,” Alfano said.
At least 58 people were killed and around 527 injured when a gunman opened fire at the Route 91 Harvest Festival, a three-day country music event, near the Mandalay Bay casino.
The gunman, identified as 64-year-old Stephen Paddock, opened fire from the 32nd floor of a Las Vegas hotel sending thousands of festivalgoers into a state of panic.
Paddock is then believed to have turned the gun on himself and was found dead in his hotel room.
The attacker had no significant prior criminal history, officials said.
Investigators are trying to piece together his background to discover the motive behind the attack.
Earlier reports stated the ISIS had claimed responsibility for the attack, but the FBI has affirmed that no connection with the international terror group has been found in the ongoing investigation.