DECATUR, Ga. (AP) — A teen was in custody Tuesday, accused of firing shots from an assault rifle at an Atlanta-area elementary school where dramatic television footage showed young students racing out of the building, being escorted by teachers and police to safety. No one was injured.

The 800 or so students in pre-kindergarten to fifth grade were evacuated from Ronald E. McNair Discovery Learning Academy in Decatur, a few miles east of Atlanta. They sat outside in a field for a time until school buses came to take them to their waiting parents and other relatives at a nearby Wal-Mart. When the first bus arrived a couple hours later, cheers erupted in the store parking lot.

The suspect, a 19-year-old man with no clear ties to the school, fired at least a half-dozen shots with an assault rifle from inside the school and officers returned fire when the man was alone and they had a clear shot, DeKalb County Police Chief Cedric L. Alexander said at a news conference.

Though the school has a system where people must be buzzed in, the gunman slipped inside behind someone authorized to be there, Alexander said. The suspect, whose identity was not released, never got past the front office, where he held one or two employees captive for a time, and was being questioned at the police department, Alexander said. No charges had yet been filed.

A woman in the school office called WSB-TV as it was happening to say the gunman asked her to contact the Atlanta station and police. WSB said during the call, shots were heard in the background. Assignment editor Lacey Lecroy said she spoke with the woman who said she was alone with the man and his gun was visible.

"It didn't take long to know that this woman was serious," Lecroy said. "Shots were one of the last things I heard. I was so worried for her."

U.S. Marshals and other law enforcement took the man into custody after the shootout. Alexander said the man had other weapons.

DeKalb County Schools Superintendent Michael Thurmond praised faculty and authorities who got the young students to safety, staying calm and following safety plans in place. All teachers and students made it out of the school unharmed.

"It's a blessed day, all of our children are safe," Thurmond said at the news conference. "This was a highly professional response on the ground by DeKalb County employees assisted by law enforcement."

Complicating the rescue, bomb-sniffing dogs alerted officers to something in the suspect's trunk and investigators believe the man may have been carrying explosives, Alexander said. Officials cut a hole in a fence to make sure students running from the building could get even farther away to a nearby street, he said.

Police had strung yellow tape up blocking intersections near the school while children waited to be taken to Wal-Mart where hundreds of people were anticipating their arrival. The crowd waved from behind yellow police tape as buses packed with children started pulling up along the road at the store. The smiling children waved back.

Regional superintendent Rachel Zeigler used a megaphone to say children were on the buses by grade level and that each bus would also be carrying an administrator, a teacher and a Georgia Bureau of Investigation officer. Relatives had to show ID, sign each child out and have their photo taken.

The school has about 870 children enrolled. The academy is named after McNair, an astronaut who died when the space shuttle Challenger exploded on Jan. 28, 1986, according to the school's website.

Jonessia White, the mother of a kindergartner, said the school's doors are normally locked.

"I took (my son) to school this morning and had to be buzzed in," she said. "So I'm wondering how the guy got in the door."

Jackie Zamora, 61, of Decatur, was at the Wal-Mart waiting and said her 6-year-old grandson was inside the school when the shooting was reported and she panicked for more than an hour because she hadn't heard whether or not anyone had been injured.

She said the school has a set of double doors where visitors must be buzzed in and show identification to a camera to be allowed in.

"I don't know how this could happen at this school," Zamora said. "There's so much security."

School volunteer Deborah Haynes said she encountered the suspect without knowing it.

She stopped by the office at the end of her shift and saw a man talking to a secretary but she did not see a gun.

"I heard him say, 'I'm not here to harm any staff or any parents or students. He said he wanted to speak to a police officer."

"By the time I got to 2nd Avenue, I heard gunshots," she said.