On the same day the Baltimore Police Department graduated the city’s future men and women in blue, the agency suspended an officer who was captured on video pummeling a man on the street. The department announced late Sunday it had accepted the officer’s resignation.In the now-viral footage, the officer and the man, whom his lawyer identified as DeShawn McGrier, can be seen talking to each other. "Don’t touch me," McGrier told the officer, who then repeatedly punched the man. The two ended up on nearby stair steps, where the officer continued beating McGrier. McGrier fell to the ground, and the officer stayed on top of him, appearing to restrain him.Interim Baltimore Police Commissioner Gary Tuggle immediately suspended the officer and ordered an investigation after the agency received videos of the confrontation."While I have an expectation that officers are out of their cars, on foot, and engaging with citizens, I expect that it will be done professionally and constitutionally. I have zero tolerance for behavior like I witnessed on the video today. Officers have a responsibility and duty to control their emotions in the most stressful of situations," Tuggle said in a statement Saturday, just hours after he honored the city’s police academy graduates.The Baltimore Police Department announced Sunday night in a tweet that Tuggle accepted the resignation of the officer:"UPDATE:The officer involved in yesterday’s incident is no longer with the BPD. Interim Commissioner Tuggle has accepted his resignation. The second officer remains on administrative duties. This remains an active criminal investigation."The incident places fresh scrutiny on a department that is supposed to be reforming its police practices and is dealing with a tumultuous year — one that has been marred by the forced departures of two commissioners and concerns that the agency’s recruits have been receiving badges and guns without an understanding of lawful police work.The agency has been going through an overhaul after the Justice Department under President Barack Obama found that its officers engaged in widespread discrimination and unconstitutional policing policies that disproportionately affected African Americans. The city has agreed to a federal consent decree, which imposes rules on policing and requires monitoring of the agency’s activities.The latest incident happened at about 11:45 a.m. Saturday, when two officers encountered McGrier in east Baltimore. The police department said that one of the officers is familiar with McGrier and that "the situation escalated" after McGrier refused to give officers identification. In the video, a second officer can be seen standing near McGrier while he is being punched. At one point, that officer, who has been placed on administrative duties while the investigation is ongoing, appeared to be trying to stop his colleague.Baltimore police said the officer who struck McGrier had been with the department for just over a year. The agency has not released his name. But Baltimore defense lawyer Warren Brown, McGrier’s attorney, identified him as Arthur Williams and said the same officer arrested McGrier in June, when his client was charged with assault, disorderly conduct and resisting arrest. A video of the June 26 encounter showed McGrier being held on the ground by the same officer, Brown said.Brown said that the Saturday encounter was a "follow-up" to the June incident, and that the officer cornered McGrier and placed his hands on him "for no justifiable reason.""What went on out there yesterday was not professional; it’s personal," Brown told The Washington Post on Sunday. "This is not police work. This is one guy beating up another guy."McGrier, who was not charged over the Saturday incident, remains in a hospital. Brown said McGrier’s jaw, ribs and nose were fractured and doctors had concerns about his ability to breathe.Brown said he is confident that the officer will be charged. The Baltimore City State’s Attorney’s Office is investigating the incident and has not commented.Mayor Catherine E. Pugh, D, said she has seen the video and has "demanded answers and accountability.""We are working day and night to bring about a new era of community-based, Constitutional policing and will not be deterred by this or any other instance that threatens our efforts to re-establish the trust of all citizens in the Baltimore Police Department," Pugh said.Sherrilyn Ifill, president of the NAACP Legal Defense and Educational Fund, called the incident "a flagrant violation" of the consent decree.The city and the Justice Department reached the agreement in 2015, after Freddie Gray died while in police custody. The consent decree, which is more than 200 pages, outlines rules on vehicle stops, searches, arrests and more. The Justice Department under Attorney General Jeff Sessions challenged the agreement, saying it had been rushed and would reduce the powers of the police department. But a federal judge in February approved the decree, citing the need to repair "the many fractures so poignantly revealed by the record."The consent decree also required the creation of an independent team of experts to monitor the police department’s compliance. That team, which is made up of experts on policing, civil rights enforcement and police reform, said in a statement that it has reviewed the video and will watch closely to see how the department "responds to and investigates this incident."The Baltimore police union did not return a call seeking comment Sunday. Lt. Gene Ryan, the union’s president, told the Baltimore Sun that "at first view" of the video, it showed "inexcusable behavior" on the officer’s part. But Ryan added that there might be more to the incident that he does not yet know.The tumult comes a few months after former Baltimore police commissioner Darryl De Sousa resigned over accusations that he failed to file federal tax returns in 2013, 2014 and 2015. De Sousa replaced Kevin Davis, whom the mayor fired in January, citing the city’s record-setting homicide rate.In February, while De Sousa was commissioner, a report raised questions about the qualification of Baltimore’s academy recruits. Sgt. Josh Rosenblatt, the academy’s head of legal instruction, told the Baltimore Sun that a third of recruits don’t have an understanding of the laws on constitutional policing, but the department gives them badges anyway.Brown, McGrier’s defense attorney, said the beating "might be Exhibit 1 in that regard.""This officer is fresh out of the academy, which makes you wonder what are they teaching them there and what type of psychological screening they employ with these cadets," Brown said.A spokesman for the police department did not answer questions about the officer’s performance while in the academy.The Baltimore Sun reported that the officer graduated from the academy in April. A video of a ceremony that month showed a graduate named Officer Arthur Williams receiving three top honors, including the Police Commissioner’s Award of Excellence and the Director’s Leadership Award. He also scored the highest, 94.88 percent, "in the categories of defense tactics, physical training and emergency vehicle operations," according to the video.—-The Washington Post’s Peter Hermann and Sari Horwitz contributed to this report.