The Clayton County Sheriff’s Office said the deputy was terminated for “excessive use of force” after a video showing him pinning and punching Roderick Walker, 26, was circulated widely on social media.

A sheriff’s deputy in Georgia has been fired after video circulated on social media showing him pinning and beating a Black man after a traffic stop, the authorities said on Sunday.

The sheriff’s office in Clayton County, just south of Atlanta, said in a statement that the deputy had been fired for “excessive use of force.” The deputy, whose name was not released, was initially placed on unpaid administrative leave after the department was “made aware of a video posted on social media involving a deputy using physical force on a man,” the sheriff’s office said.

Cellphone footage of the confrontation, which took place on Friday, was recorded by at least two bystanders and shared widely on social media. The videos show two deputies, who are white, pinning and beating the Black man, Roderick Walker, 26, in the street.

Shean Williams, a lawyer representing Mr. Walker and his family, demanded that he be released from the Clayton County Jail in Jonesboro, Ga., where Mr. Walker remained in custody on Sunday on two counts each of battery and obstructing or hindering law enforcement officers, according to jail records.

At a news conference on Saturday night, Mr. Williams said that Mr. Walker and his girlfriend returned a rental car on Friday and then paid a man to take them to their next destination. Mr. Williams said the car they were riding in was pulled over because it had a broken taillight.

The deputies asked Mr. Walker for his identification even though he was not the driver, Mr. Williams said. The deputies “became upset when he inquired — like every American citizen has the right to inquire — ‘Why are you asking me for my ID? I’m not driving, and I have not done anything wrong,’” Mr. Williams said.

“The next thing you know — and you’ve seen on the video — he’s attacked, beaten in his face, throughout his body,” Mr. Williams said. “He is choked, he is unable to breathe.”

At one point, the videos show one of the deputies punch Mr. Walker several times in the head. Both deputies appear to be on top of Mr. Walker, using their body weight to apply pressure to his neck and torso.

Mr. Walker appears to say “I can’t breathe.” He also appears to lose consciousness as the deputies roll him over to reveal his bloodied face. A woman who was recording one of the videos can be heard screaming throughout the interaction, and an officer asks her to return to a car as she pleads with them.