JOHANNESBURG (AP) - They bound his hands to the rear of a van, and then sped off, dragging the slender taxi driver along the pavement as a crowd of onlookers shouted in dismay. The man was later found dead. A gut-wrenching video of the scene is all the more disturbing because the men who abused the Mozambican immigrant were uniformed South African police officers and the van was a marked police vehicle. The graphic scenes of the victim struggling for his life shocked a nation long accustomed to reports of police violence. The visuals of the incident are horrific, disturbing and unacceptable. No human being should be treated in that manner," said South African President Jacob Zuma. It sparked immediate outrage about police behavior. "They are there for safety, but we as a people fear them more," said Johannesburg resident Alfonso Adams. You don't know who to trust anymore. Some of those in the crowd who watched the scene unfold in the Daveyton township east of Johannesburg shouted at the police and warned that it was being videotaped. The police did not seem at all concerned by all the witnesses and the presence of cameras as they tied Mido Macia, a 27-year-old from neighboring Mozambique, to the back of a police vehicle, his hands behind his head. Macia was found dead in a Daveyton police cell late Tuesday. The video can be seen at: http://bit.ly/ZDOj0A A murder probe is underway on the evidence that Macia suffered head and upper abdomen injuries, including internal bleeding, the Independent Police Investigative Directorate, the police watchdog agency, said Thursday. The injuries could be from the dragging and he could also have been beaten later in police custody. The allegations are that he was dragged behind a vehicle and his head was bent on the police vehicle. There are also allegations of assault," said the investigative unit's spokesman Moses Dlamini. The video evidence of the abuse renewed concerns about brutality, corruption and other misconduct by a national police force whose reputation has suffered in recent years amid reports that many officers lack training. As horrific as it is, it is not exceptional. Hardly a week goes by without such stories of brutality," said Jacob van Garderen, national director of Lawyers for Human Rights. Then Macia allegedly assaulted a constable and took his weapon before he was overpowered, the police investigative unit said. Macia was found dead in a cell over two hours later by another policeman, according to the watchdog agency. National Police Commissioner Riah Phiyega "strongly condemned" what happened. South Africans are "urged to remain vigilant and continue to report all acts of crime irrespective of who is involved," said Phiyega in a statement. Phiyega has tried to upgrade the reputation of the South African police since her appointment last year. The problems, though, are immense for a police force that has expanded from some 120,000 to almost 200,000 over the last decade, "often failing to match the increase in quantity with sufficient quality," said Johan Burger, who served for 36 years on the force before becoming a senior researcher at the Institute for Security Studies. Several experts contacted by The Associated Press also said that in recent years there has been an increasing willingness to use a shoot-to-kill approach to the crime and violence. An average of 860 people a year died in police custody or as a result of police action between 2009 and 2010, up from 695 a year from 2003 to 2008, according to Burger of the security studies institute. Further staining the reputation of the police is the Marikana shootings when, on Aug. 16, 2012, a line of South African police opened fire on a crowd of striking miners, killing 34 at a platinum mine northwest of Johannesburg. A judicial commission is investigating allegations that many were killed in a rocky hill, near the much-filmed initial scene of the attack, shot in the back as they tried to escape. Associated Press Writer Michelle Faul contributed to this story.