The officer had an immediate explanation after shooting an unarmed black man during a traffic stop in South Carolina: He said he fired in self-defense after a struggle over his stun gun.
But his initial claim points to a policing paradox that has civil rights advocates alarmed. Promoted as tools to avoid lethal force, stun guns can sometimes become part of a deadly equation.
"Officers need to be spending more time de-escalating situations, instead of resorting to the use of this very convenient tool," said Emma Andersson, a staff attorney with the American Civil Liberties Union. "The jury's still out on whether or not its lethal force, but it's not nothing -- it's very dangerous."
Officer Michael Slager was charged with murder and then fired from the North Charleston Police Department after a bystander's iPhone video captured him shooting a fleeing Walter Scott in the back after failing to subdue him with a Taser.
Just two days before Scott's April 4 death, a 73-year-old reserve sheriff's deputy who said he thought he was firing his stun gun instead fatally shot another black man, 44-year-old Eric Harris, after a chase in Tulsa, Oklahoma. A video of that killing, released Friday, is raising new concerns about how Tasers can have deadly consequences.
The Associated Press found at least a half-dozen other fatal shootings of black men by police with stun guns involved since 2012.
These immobilizing weapons are useful, but can give officers "a really false reassurance that you have more control over a situation than you do," said Eugene O'Donnell, a former New York City police officer who now teaches at the city's John Jay College of Criminal Justice.
Stun guns are used by more than 15,000 U.S. law enforcement and military agencies, according to a 2011 federal National Institute of Justice report. Taser, a leading manufacturer, says it has sold more than 800,000 in the last 20 years to law enforcement agencies, which have used them more than 2.3 million times.
The overall record shows that Tasers are "safe, effective and accountable," said Steve Tuttle, a spokesman for Scottsdale, Arizona-based TASER International Inc.
"Our success rates are tremendous, but it's not a magic bullet," he added. "There is no magic bullet,"
While video of the North Charleston and Tulsa shootings has raised a national outcry, less attention was paid to other killings of black men by police after stun guns were involved, including:
-- Lamont Harmon, 47, was killed after walking near a gas station where Sacramento County, California, deputies found a stolen car in 2012. The official version is that he fled when deputies tried to pat him down; a stun gun didn't stop him; and then a deputy fired four bullets into him because he thought Harmon was reaching for a gun in his waistband. The deputy "firmly believes that his use of force was justified," the county said. Harmon's mother, Annie, has sued for $10 million. "Our contention is that this shooting was wholly unjustified and there was no reason for these officers to fear for their lives," says her lawyer, Dewitt Lacy.
-- Lavall Hall, a 25-year-old schizophrenic, was killed in February by an officer in Miami Gardens, Florida. Hall's mother had reported her son was having a violent episode; authorities say he refused commands to stop swinging a metal broom. His family said officers also used stun guns at least twice with no effect. A police dashboard camera recorded an officer saying "get on the ground, or you're dead" before five shots are fired. The family wants an independent investigation.
-- Kaldrick Donald, a 24-year-old who wasn't taking medication for mental problems, was killed in October after his mother called police in Gretna, Florida. Donald punched a sergeant in the face and kept hitting despite a stun-gun shock. The sergeant pulled Donald into a bathroom and then became stuck when the floor caved in, and was justified in firing nine shots into his body, the Florida Department of Law Enforcement determined. Donald's mother, Juanita, told WCT-TV that her son had been walking away before the sergeant "just grabbed him, and he Tased him."
"He was like, 'I had to.' I said, 'No, you didn't have to,'" said Juanita Donald, who has sued.
Peltz reported from New York and Williams from Detroit.