The dashboard camera video shows what appears to be a routine traffic stop -- until it is not.
Experts who spoke with the Los Angeles Times were struck by how courteous the initial exchange was between North Charleston, S.C., Police Officer Michael T. Slager and motorist Walter L. Scott.
They agreed that Scott should not have run, but disagreed about whether Slager should have chased him. And they noted that when Slager shouted, "Taser! Taser! Taser!" it meant he was about to use the non-lethal weapon.
In the video, released Thursday by the South Carolina Law Enforcement Division, Scott pulls into a parking spot at an Advance Auto Parts store in North Charleston. Moments later, Slager walks toward the car.
"The reason I stopped you is your brake light is out," Slager says. He asks for Scott's license and registration.
Scott says he doesn't have the registration or insurance card because he is in the process of purchasing the car, but he appears to hand Slager his driver's license. The officer takes it to his police cruiser, telling Scott to wait inside his own car.
A few minutes later, however, Scott gets out and runs away. A cellphone video taken by a passerby picks up the encounter, apparently as Slager is trying to use his Taser on Scott.
Slager is charged with murder.
But how did everything go so wrong? Neither man raised his voice nor made any move toward the other. Neither appeared hostile.
"I was a bit surprised at how courteous [the officer] was," Terry L. Cooper, an expert in ethics for law enforcement officers at the University of Southern California, told The Times. "That was done very well."
Lisa Graziano, an associate professor of criminal justice at Cal State Los Angeles, agreed. "The behavior of the officer came off as standard. From what I saw, he seemed to handle it very professionally."