Officer Michael Slager stared blankly during his bond hearing on Tuesday evening. He appeared from jail via video link, dressed in an inmate’s uniform of black and grey stripes.

Judge Alvin Bligen read Slager his rights in monotone before telling him he was charged with murder and therefore unable to grant bail.

“Are you married?” Bligen asked.

“Yes,” came the reply.

“Children?”

“I have two stepchildren and one on the way,” he said, pursing his lips into a half smile.

Just hours before Slager, had been a free man and a serving officer – albeit one on paid administrative leave.

At around 9.30am on Saturday, Slager had shot dead 50-year-old Walter Scott and claimed that Scott had “tried to overpower him” and “take his Taser”. But video published on Tuesday revealed an entirely different narrative – that Scott, a black man, had in fact been running away at the time he was shot, a good 15ft at least before Slager, who is white, had fired. It appeared Slager may have dropped a Taser next to Scott’s body.

The tide immediately turned against the officer. His attorney dropped the case shortly after seeing the video; his professional association refused to pay any legal costs, accusing him of “tarnishing ... the badge”; the chief of his department said he was “sickened” by what he saw. He was abandoned by the institutions that had earlier protected him.

As the cold-hearted reality of Slager’s actions that Saturday begin to sink in, little is known about the officer’s prior history, and a number of questions still surround his conduct that day.

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The 33-year-old was born in November 1981 and attended Lenape high school in the small township of Medford, New Jersey, where he graduated in 2001. A photograph from his high school yearbook shows Slager smiling alongside a line of other grinning faces, but he appears to have made little impact on his former classmates.

“I do not recall Michael from my high school days,” said Kurt Minuto, the class president in Slager’s sophomore year. “I have no recollection of that person at all,” said Frank Iannucci, who was the vice-president.

According to documents obtained by NBC, Slager spent time working as a waiter before joining the US coastguard.

Records show he spent time living on Cocoa Beach, Florida, on a road lined with palm trees a few hundred feet from a resort-filled beach. He appears to have moved to South Carolina in 2008 and, according to the records obtained by NBC, applied to join the North Charleston police in 2009, swearing his oath on 1 March 2010. His former attorney, David Aylor, told the Guardian that Slager was honorably discharged from the coastguard prior to this.

Calls to Slager’s relatives, neighbors, former roommates and friends have all been unreturned or unanswered. An online campaign to provide “support funds” has raised less than $800.

Slager’s wife, Jamie, eight months pregnant with Slager’s first child, has deleted her Facebook page. A photograph on another of her social network pages shows Slager smiling with who appear to be his two young stepchildren at his side. At a press conference on Wednesday, North Charleston mayor Keith Summey said the city would continue to pay her medical insurance until the child is born. Calls to her cellphone went unreturned.

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According to the personnel documents obtained by NBC, Slager held a relatively exemplary training record. In March 2010, shortly after joining the force, he is described as demonstrating “great officer safety tactics” in confrontations with suspects. He routinely passed annual training tests, including those related to firearm use. In February 2011 he earned a perfect score in Taser certification test questions, according to NBC.

Since the death of Walter Scott, details on a past complaint have been revealed as the victim of an alleged excessive use of force incident from September 2013 has come forward.

Mario Givens, 33, claims that Slager knocked on his front door at 4am and Tasered him even though he had raised his hands as the officer commanded.

“I didn’t know what was going on; he never said nothing,” Givens told a news conference on Thursday. “He didn’t even announce he was police, he just pounded on the door.”

Givens filed a complaint at the time, but says he never heard back from the police department. He has indicated he will now sue the department.

Protesters argue that the Scott murder is emblematic of broader race-related problems within the North Charleston police department, which employs less than 20% black officers in a city where almost half the residents are African American.

When Summey was asked about this disparity, he fumbled a response indicating there was not enough of a pool to recruit, much to the ire of assembled protesters who could be heard heckling him.

Since Scott’s death it has also emerged that the second officer on the scene, Clarence Habersham – an African American – is the subject of a separate lawsuit in which the complainant states he was stomped in the face while handcuffed by a group of officers.

Givens claimed that Habersham was also present at the 2013 Tasering incident.

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It remains unclear if Slager ever provided a statement to the North Charleston police department, or outside investigators, commissioned to examine the Scott shooting. On Thursday, authorities released dashcam footage showing Slager and Scott interacting before Scott fled. And eyewitness Feidin Santana said he saw the two on the ground before he filmed, noting that Slager “had control of the situation” and Scott was simply trying to escape being Tasered.

There remain questions over who the passenger was in Scott’s car when he was pulled over initially by Slager for a traffic violation. And it is also unclear why Scott had fled from the car – although some have speculated it related to a warrant related to unpaid child support.

Slager’s next court appearance is not until 21 August. He has recruited new lawyers, who have yet to make a statement on his behalf.