A Charleston, South Carolina, judge declared a mistrial Monday in the case of a white South Carolina police officer on trial for the video-taped shooting of Walter Scott, a 50-year-old black man. The video was secretly taken last year by a passerby, and it has been viewed online millions of times. This week, after four days of deliberations, the 12-member jury announced it was hopelessly deadlocked.

On trial is Michael Slager, a 35-year-old now-fired North Charleston officer. He's accused of killing Scott by shooting the man in the back. Scott was pulled over in April 2015 for a routine traffic stop—a tail-light that was not working. He had a warrant for his arrest and fled the scene, prompting a chase. The officer testified that there was a brief altercation in a park over his Taser, and the cop then shot Scott five times as he fled. Slager has said he acted out of "total fear."

Charleston County's top prosecutor vowed a retrial. "We will try Mr. Slager again," Scarlett A. Wilson said in a statement.

The killing is yet another instance of police shooting a black man in the US. According to various watchdog sources—the Washington Post, The Guardian, and the Killed by Cops database—between 706 and 844 people have been killed by US cops during the first nine months of 2016. Of that total, the North Carolina ACLU notes there were 194 deceased black Americans.

Jurors in this case had the option of a murder conviction, which would have netted Slager a 30-year-to-life term, and a voluntary manslaughter charge. That charge carries a term of two to 30 years, and it's designed to allow jurors to convict on a lesser charge that the officer killed out of the heat of passion after provocation.

Defense attorneys previously unsuccessfully tried to have the video excluded. They asked for a mistrial on Friday after a juror said that he or she could not reach a guilty verdict. Judge Clifton Newman told jurors, who have been on the case for a month, to continue deliberating. After a weekend break and a few hours deliberating on Monday, the jury asked the judge why the officer was charged with voluntary manslaughter and whether the self-defense standard is the same for an officer and a member of the public. Shortly thereafter, the jury said it was deadlocked and could not reach a unanimous verdict.

"I want to thank your for your service," the judge said after excusing them.

Slager has been free on a $500,000 bond since January. While he now faces a retrial on the state charges, federal charges against him are pending. Those include allegations of civil rights violations and obstruction.

The North Charleston police agency had defended Officer Slager until the footage surfaced. The South Carolina man who used his phone to record a video of Slager fatally shooting Scott said that another officer who arrived on the scene ordered him to stop recording. But after the film went viral days later, the police agency changed its public story and stopped supporting Slager.

The city of North Charleston has settled a lawsuit with the Scott family for $6.5 million.

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