U.S. Education secretary Arne Duncan praised Ronald E. McNair Discovery Learning Academy leaders Friday for their response when an armed intruder walked into the school.

On Tuesday, Michael Brandon Hill walked into McNair Academy’s front door with nearly 500 bullets and an assault rifle. The school went into lockdown and the school’s bookkeeper, Antoinette Tuff, was able to keep him in the front office until police arrested him. No one was injured.

Hill is being held without bond and faces several charges.

On Friday, during a video conference with McNair’s staff, DeKalb County administrators and school board members, Duncan described the school’s leaders as heroes.

He also said he was concerned about mentally ill patients getting access to guns.

“As a parent, I have two young children in elementary school. I want to thank you for your extraordinary work this week,” said Duncan. “We go into education to transform lives, not to save lives, but your team this week saved lots and lots of lives.”

DeKalb’s interim superintendent, Michael Thurmond, also took the opportunity to praise the staff for properly executing the school’s safety plan. But he said while the plan went well, they will still review Tuesday’s events with security experts to see what they can do better.

“We’re going to evaluate the plan in a deliberate way so we can find out what we can do to make the district’s safety plan even better,” Thurmond said.

On Tuesday, soon after an intruder alert was broadcast over the loudspeaker and the school was in lockdown, teachers quickly locked their classroom doors, turned off the lights and crowded students into corners. Some sent text messages to each other letting them know the lockdown was not a drill.

“His demeanor and the fact that he shot his gun made it look like he was agitated,” said Malcolm Quillen, the school’s cafeteria manager, who ran into the gunman after checking his mail. “I wanted to do what he told me to do.”

The school’s principal, Brian Bolden, made the staff practice the lockdown drill monthly, Bolden said Friday.

“I wanted our staff to be ready to make quick decisions,” he said.

Since the incident, the district has gotten praise from officials around the country. Tuff was recently invited to the White House, and the school’s staff and students recently received an invitation to attend an Atlanta Braves baseball game.

While the conversation with Duncan lasted no more than 10 minutes, Thurmond took the opportunity to invite the secretary to visit DeKalb schools for some “Southern hospitality.”

“I might actually take you up on that,” Duncan said.