The Kenosha police officer who shot Jacob Blake in the back seven times last month told investigators he thought Blake was trying to abduct one of his own children and opened fire because Blake started turning toward the officer while holding a knife, the officer’s lawyer contends.

Blake was paralyzed from the waist down.

In a summer marked by nationwide protests over police brutality and racism, the shooting of a Black man by a white officer sparked outrage and led to several nights of protests and unrest, including a night in which authorities say a 17-year-old who came to Kenosha from Illinois shot and killed two protesters and wounded a third.

Brendan Matthews, the attorney for Officer Rusten Sheskey and the Kenosha police union, told CNN that when Sheskey arrived at the scene on 23 August in response to a call from a woman who said Blake was at her home and shouldn’t be there, he heard a woman say: “He’s got my kid. He’s got my keys.”

Sheskey saw Blake put a child in the SUV as he arrived but didn’t know two other children were also in the back seat, Matthews said. He said Sheskey told investigators he opened fire because Blake “held a knife in his hand and twisted his body toward” the officer, and that he didn’t stop until he determined Blake “no longer posed an imminent threat”.

Matthews said if Sheskey had allowed Blake to leave and something happened to the child, “the question would have been ‘Why didn’t you do something?’”

Cellphone video shows Sheskey and another officer follow Blake with their guns drawn as he walks around the front of the parked SUV, opens the driver’s side door and lean into the vehicle. Sheskey then opens fire.

Ben Crump, an attorney for Blake’s family, did not immediately respond to an email seeking comment. He previously said Blake was only trying to break up a domestic dispute and did nothing to provoke police, adding that witnesses didn’t see him with a knife.

Blake’s uncle Justin Blake said on Saturday the allegation that Blake was attempting to kidnap his own child was false, the Kenosha News reported.

“That’s ridiculous,” Justin Blake said. “It’s gaslighting. Outright lies.”

The bystander who recorded the shooting, 22-year-old Raysean White, said he saw Blake scuffling with three officers and heard them yell: “Drop the knife! Drop the knife!” White said he didn’t see a knife in Blake’s hands.

The Wisconsin department of justice, leading the investigation, said a knife was found in the vehicle, but didn’t say if Blake had been holding it or if police knew it was there before Sheskey shot him.

In a statement released by Matthews on behalf of the police union, the lawyer said Blake was armed with a knife but officers didn’t see it until Blake reached the passenger side of the vehicle.

The mother of the three children, who called police, filed a complaint against Blake that led to felony charges accusing him of sexually assaulting a woman in May.

Blake, who was wanted on a warrant for those charges when police arrived at the scene, pleaded not guilty earlier this month via video from from his hospital bed. A trial date was set for 9 November.

Sheskey and the other two officers who were at the scene were placed on administrative leave pending the outcome of the investigation.