ABC News(LANCASTER, Pa.) — A crowd of protesters gathered on the steps of an old courthouse in southern Pennsylvania on Friday evening, one day after a video posted on social media showed a local officer using a Taser on an unarmed black man sitting on a sidewalk.The dozens of demonstrators outside Lancaster County Courthouse were calling for an end to police brutality and an external investigation into the police officer’s use of force.“I think there needs to be higher police accountability to the community,” one of the protesters, Brandon Roe of Lancaster County, told ABC affiliate WHTM. “It just shows the numbers in solidarity that this movement has, that we need more respect for people’s rights, the rights of the accused, the rights of our communities to be treated with respect.”“It’s not OK for police to treat some people different than others,” another protester, Malinda Harnish Clatterbuck of nearby Fayette County, told WHTM. “When it’s a systematic problem, then I think there has to be a systematic response.”Sean Williams, the 27-year-old shown in the video having the Taser used on him, was at the rally Friday night. He declined to speak to reporters on camera, but thanked the media for being there, according to WHTM.The widely-shared video of the incident, taken by a bystander, shows at least two police officers ordering Williams to sit down on a sidewalk curb in Lancaster. Williams complies.The officers then repeatedly direct Williams to put his legs “straight out” in front of him.“Legs straight out or you’re getting tased,” a male officer standing behind Williams can be heard saying in the video, with his Taser drawn.“Put your legs straight out and cross them now,” a female officer yells.Williams appears to begin following the officers’ orders by straightening his legs but then folds them back again. That’s when the male officer fires his Taser.Williams writhes in pain on the ground, with the Taser’s dart-like probes attached to his back. The male officer then orders Williams to stay flat on his stomach with his “arms out like an airplane.”More officers then arrive on the scene, and Williams is placed in handcuffs.According to the police report, the encounter with Williams stemmed from a 911 call authorities received on Thursday morning reporting that a man “with a bat” went after a group of three other persons.Lancaster Police Officer Shannon Mazzante responded to the call and came across a group of three individuals “telling a male to get away from them,” the report said.Mazzante told the man, identified by police as Williams, to sit down “several times” but he didn’t comply. Williams wouldn’t leave a woman in the group alone and “kept repeating that he wanted a specific item, his Social Security card, from her,” according to the report.Lancaster Police Officer Philip Bernot arrived on the scene soon after and warned Williams that a Taser would be used if he didn’t listen to their orders.“Williams was instructed to stick his legs straight out in front of him and to cross his ankles. This is done as a measure of control to ensure that if someone is going to flee or offer physical resistance, they will have to move their legs under them to do so. Noncompliance is often a precursor to someone that is preparing to flee or fight with officers,” the report said.The report said Bernot deployed the Taser after Williams “failed to follow instructions.” Williams was then taken into custody “without further incident or use of force,” according to the report.The group that had been apparently telling Williams to get away told police that they knew him and he “had been exhibiting increasing erratic behavior over the previous few days.” They said Williams had been outside a residence earlier and wanted to fight with them. But the group said they did not see Williams with a bat, and no bat was found at the scene, the report said.Juan Almestica, the bystander who took the video, told ABC News that he went outside his home after hearing a commotion. Almestica said the man had his hands up and told police, “I don’t want no trouble.”“I could see the officer was still being aggressive with him and aiming his Taser, so that’s why I decided to start filming,” Almestica told ABC News in a telephone interview Friday. “One of the officers is telling him to put his legs straight, and another one is telling him to cross his legs. There were so many people shouting at him, he didn’t know what to do. Then they tased him because they said he wasn’t listening.”Upon apprehending Williams, police learned that there was an outstanding criminal warrant for his arrest for possession of a controlled substance and public drunkenness. Williams was taken into custody on the warrant and transported to the police station, according to the police report.Williams was checked by emergency medical services, “as is protocol” with every use of an electronic control device, the police report said. He was later released on unsecured $5,000 bail.Lancaster Mayor Danene Sorace said an investigation into the incident is underway.“Like you, when I saw the video I was upset by it, and it is of great concern to me,” Sorace said in a video posted to her Facebook page Friday. “We take the use of force very seriously. There is an investigation that has already commenced.” Copyright © 2018, ABC Radio. All rights reserved.