Authorities kept a man suspected in a triple shooting at a shopping mall under police guard Sunday in a hospital, and said charges were expected.

An off-duty U.S. Secret Service agent who tried to break up the melee and returned gunfire also was recovering from a gunshot wound to the leg, officials said.

Police did not release the name of the 18-year-old suspect, because detectives have been unable to talk to him and verify his identity. Police would only say he was from Annapolis and remained in stable condition.

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"We have the shooter guarded at the hospital and he is going to be in custody," said Officer Sara Schriver, an Anne Arundel County police spokeswoman. "He is going to be charged, so it's not like we have somebody at large."

The off-duty agent was in the Westfield Annapolis mall with his family at about 7:15 Saturday night when he saw a group of about eight young males acting disorderly in the food court area, police said. When he saw several of them assault another, he intervened and tried to stop it.

One of the people involved in the altercation pulled out a handgun and shot the agent, who then drew his service weapon, shouted that he was a police officer and fired back, police said. The suspect was shot twice in the upper body and apprehended by police officers.

Under federal law, Secret Service agents are allowed to carry a gun when they are off duty.

Kim Bruce, a spokeswoman for the U.S. Secret Service, declined to identify the off-duty agent. She said he had surgery on his leg Saturday night.

"Right now, he's in stable condition," she said. "He got shot once in the leg."

The third person who was shot was identified as 16-year-old Tahzay Brown, who was treated and released from a hospital before midnight Saturday, a hospital spokeswoman said.

Brown is a student at Annapolis High School, where he was involved in one of several fights that have drawn police to the school this year, his mother, Tanjala Brown, told The [Baltimore] Sun. She told the newspaper her son was jumped in September, and police never identified who attacked him.

On Friday, seven students were arrested after two fights at the school. Schriver said police were looking into the possibility that the school fighting may have been a motive.

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