(CNN) -- The Baltimore police officer caught on video punching a man for 12 seconds has "a history of antagonizing and aggravating" that civilian, the man's attorney said Monday.
Warren Brown represents Dashawn McGrier, who got pummeled by the police officer Saturday morning. Brown said his client was arrested by the same officer in June and charged with assaulting the officer, disorderly conduct, obstructing and hindering, and resisting arrest.
A trial date for the case has been set for later this month.
The officer, Arthur Williams, was a newly sworn probationary officer, Baltimore police union president Gene S. Ryan said. Williams resigned amid outrage over the attack.
Brown said that during the June incident, his client was trying to restrain a young woman encountered by the officer. The cop then turned his ire to McGrier, grabbed him off a bicycle and threw him to the ground, the attorney said.
"This officer has a history of antagonizing and aggravating my client," Brown said.
Baltimore police said one of the two officers involved in Saturday's incident was familiar with the man beaten in the video. But BPD did not identify which officer knew the man. And it has not corroborated the allegations by Brown.
CNN's attempts to reach Williams have not been successful.
Video of Saturday's attack showed a second officer witnessed the punching but did little to intervene. Police said that officer has been reassigned to administrative duties pending an investigation.
The state attorney's office has been notified, Baltimore police said.
What led up to the attack
The incident began around 11:45 a.m. while officers were working on "a crime suppression detail related to crime in the area," Baltimore police spokesman T. J. Smith said.
"Two officers encountered a man, whom one of the officers is familiar with," police said.
"After the first encounter, officers released him and ... approached him again to provide him a citizen's contact sheet," police said.
Smith said officers are required to fill out a contact sheet any time they talk to a citizen in relation to any type of investigation, no matter how brief the encounter.
"When he was asked for his identification, the situation escalated when he refused," police said.
What happened next
Bystanders capture video of McGrier screaming in the officer's face.
"For what?!" McGrier yells at Williams.
The officer responds by shoving the man backward against a brick wall.
"Don't touch me!" McGrier yells, slapping the cop's hand away.
Then the video gets really ugly.
The officer starts throwing punches and continues pummeling McGrier for the next 12 seconds.
Both men eventually fall to the ground and Williams pins McGrier down with his arm across his neck. McGrier's blood starts pooling on the sidewalk.
A city trying to recover
What happened this weekend marks the latest controversial use of force against a black person by police.
The Baltimore officer who attacked the man is also black. So is another officer who witnessed the attack.
The city is still dealing with the aftermath of the 2015 death of Freddie Gray, who died in custody a week after a police encounter. Days of peaceful protests over Gray's death devolved into riots, with assaults on police, looting, arson and the devastation of businesses.
A federal investigation eventually determined the Baltimore police department engaged in unconstitutional treatment of the city's black residents as well as excessive use of force.
In January 2017, the city agreed to a consent decree, with sweeping reforms proposed by the Justice Department.
After Saturday's attack, Interim Police Commissioner Gary Tuggle suspended the officer before the officer resigned.
The acting police chief said he had "zero tolerance for behavior like I witnessed on the video."
"Officers have a responsibility and duty to control their emotions in the most stressful of situations," Tuggle said.
The Baltimore Police Consent Decree Monitoring Team -- an arm of the US District Court for Maryland -- said it'll be closely watching how BPD responds to and investigates the incident.
"This is an important moment for the Baltimore Police Department," Consent Decree Monitor Kenneth L Thompson said in a statement.
"It is an opportunity for the Department to show the Monitoring team, the Court, and the community that when its officers are involved in an incident that raises serious questions about compliance with Department policies regarding the use of force ... it will move swiftly to conduct a thorough, transparent, and fair investigation."
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