The Florida sheriff leading a state commission on the Parkland high school massacre says there were multiple opportunities to stop Nikolas Cruz during the attack – if only someone had confronted him with a gun.

Sheriff Bob Gualtieri of Pinellas County, citing surveillance footage taken from inside Marjory Stoneman Douglas High School, told a New York Times reporter Thursday that Cruz had to stop firing his AR-15 rifle several times in order to reload.

"If he had somebody in there with a gun, they could have mitigated this," the sheriff was quoted as saying. "There were opportunities for staff to have intervened if they had been armed."

Cruz, a 19-year-old former student at Stoneman Douglas, is charged with killing 17 people in the Valentine's Day attack.

Gualtieri added that during one of the reload breaks, a teacher was able to move his students to safety.

"There were several other times when he was in that school that his gun was empty," he also told the New York Times.