Jesus Campos was identified as the security guard at the Mandalay Bay Resort and Casino, said David Hickey, president of the union that represents the hotel's security guards. He was uncertain whether Campos was armed at the time.
Campos is out of the hospital, but is expected to have surgery at a later date to remove a bullet, Hickey told CNN's Wolf Blitzer.
When reached by ABC News
, Campos said he was fine. "I was just doing my job," he said.
Campos' actions may have distracted Paddock, possibly saving lives of many people below at the country music festival. The shooter killed 58 people and the attack left nearly 500 concertgoers wounded.
Paddock began firing at concertgoers from his 32nd-floor suite beginning 10:05 p.m. Sunday, according to police.
Campos had been in the building, patrolling the halls and was sent to the area of commotion. When he got to the shooter's floor, Campos found the stairwells had been barricaded and had to use the elevator, Hickey said he was told by local union officials.
When Campos approached Paddock's suite, the shooter "fired through the door, striking Mr. Campos in the upper right thigh," said Hickey who is president of the International Union, Security, Police and Fire Professionals of America.
He faced well over 200 rounds, said Sheriff Joseph Lombardo of the Las Vegas Metropolitan Police on Wednesday. "It's amazing that that security guard didn't sustain additional injury."
After being shot, Campos spoke with police officers at 10:18 p.m., giving them the shooter's exact room and key pass.
"His bravery was amazing because he remained with our officers, providing them the key pass to access the door and continued to help them clear rooms until our officers demanded he seek medical attention," said Lombardo.
Clark County Undersheriff Kevin McMahill also commended the security guard as "very heroic."
When asked why he thought Paddock stopped shooting at concertgoers, McMahill said Tuesday he believed Paddock's attention had been diverted as he fired at the security guard.