The attorney for a Cottage City teenager who was arrested Friday said surveillance cameras captured a Prince George’s County police officer hitting his client with a gun in such a way that the weapon discharged.

Jimmy Bell, the defense attorney, said he had not seen the video but had been briefed about it by those who had. A law enforcement source who saw the video corroborated his account, saying it shows an officer approach the teenager, draw his weapon and strike him in the head. At some point, the gun fired but no one was injured, police said.

On Tuesday, police announced that they were dropping some charges against the teenager after video evidence called into question the account officers provided. They said they were referring the case to the county state’s attorney’s office, which is conducting an investigation into the officers’ conduct.

The incident began about 9:40 p.m. Friday, when officers in the Brentwood area saw two people — at least one wearing a mask — go into the Lowest Price Gas station convenience store, authorities have said.

According to the account police first gave in charging documents, officers thought that the men were about to rob the store. One of the men, 19-year-old Ryan Keith Dorm, punched a detective and then ran, according to the documents. Another detective, Donald Taylor, chased him and saw what he thought was a gun fall from Dorm’s waistband, the charging papers allege. He drew his gun, and Dorm “charged towards” him and “attempted to disarm him.” The encounter caused Taylor’s gun to fire, according to the documents.

Dorm was charged with two counts of second-degree assault, three counts of second-degree assault on a law enforcement officer and resisting arrest. A spokesman for Prince George’s State’s Attorney Angela Alsobrooks said prosecutors would drop one second-degree assault charge and two charges of second-degree assault on a law enforcement officer. Dorm remains jailed on a $15,000 bond.

Police said that Taylor and an officer who was a witness were suspended with pay. Vince Canales, president of the Fraternal Order of Police Lodge 89, declined to comment on their behalf.

Carlos Acosta, the police department’s inspector general, said detectives still “believe that crimes were committed” but would not elaborate. Bell denied that his client committed any crimes.

The other man, Brion Elzie, 20, of Colmar Manor, said that he and Dorm went to the store to buy snacks and that he was wearing a ski mask because it was cold. He said he was not sure why Dorm ran.

“We wouldn’t even put ourselves in that position,” Elzie said. “We come to that store every day, and we know the people that work in there.”