The two were struggling with their arms between them and the ground.
"They were fighting for the gun, really," Bauermeister said.
McHugh yelled he had the weapon, and Sciacca said it was in his right hand, the principal said.
Bauermeister placed one knee on McHugh's shoulder and the other against his elbow. Using that as leverage, he pried the pistol out and threw it away, the principal said.
"When we got the gun away from him, it was like he relaxed," Bauermeister said. "It was really done at that point."
They held McHugh for a short time until police arrived and took him into custody. Bauermeister said it felt like just a few moments compared to the seeming eternity of the tussle.
"When we were wrestling with him, I'm sure it wasn't more than five or 10 seconds, but it felt like a really long time," Bauermeister said.
It wasn't until police told them later the gun was a BB gun that the two administrators knew they weren't confronting someone with a deadly weapon.
Even then, the thought that they were possibly risking their lives hadn't entered his mind, Bauermeister said.
"I think we were both kind of numb at that point to tell you the truth," he added.
Charges are pending against McHugh, who is scheduled to appear in court Wednesday, and students have been on their President's Day holiday since the confrontation.
Three days after the incident, Sciacca said he was still surprised by his own reaction.
He said the Newport-Mesa Unified School District's new plan for dealing with intruders may have affected him.
Exactly two weeks before the incident, Bauermeister had briefed Estancia staff on the district's new "run, hide, act" response to threats.
After the Sandy Hook Elementary School shooting in Newtown, Conn., school board members began reevaluating their procedures for armed intruders.
This month, they decided the last resort in those dire situations after running and hiding is to physically confront a threat.
Bauermeister told teachers their job is to rush students away, but he warned them they would see a small group of people running in the opposite direction.
"We know that's our job," Bauermeister said. "It's something any parent would do for their kids, and those are my kids."
Estancia will host a parents meeting to discuss the incident at 7 p.m. Monday in the choir room.