There were just 10 seconds between US police spotting a teenager with what they thought was a rifle and opening fire on him, it’s emerged.

The drama unfolded as Andy Lopez Cruz, 13, was walking in a field on his way to a friend’s house in Santa Rosa, California.

Police said they called for him to drop what turned out to be a toy replica gun, before firing several rounds from their handguns.

He died at the scene.

Now police investigating the shooting have revealed a timeline of events. There were 10 seconds between officers spotting the boy and opening fire and a further 16 seconds before medical assistance was called.

A post-mortem has revealed seven bullets were lodged within the boy’s body.

The officers involved in the shooting have been placed on “administrative leave”.

The tragedy has reignited calls in the community for creation of civilian review boards to examine such incidents.

“People have to do something,” said Elbert Howard, a founding member of the Police Accountability Clinic and Helpline of Sonoma County. “He’s a child, and he had a toy. I see that as an overreaction to shoot him down.”

An advisory panel of the US Civil Rights Commission urged Sonoma County to create civilian-review boards in 2000 following eight fatal officer-involved shootings in less than three years, but that recommendation went unheeded.

As many as 200 mourners gathered on Thursday around a makeshift memorial consisting of flowers, balloons, teddy bears and pictures of the boy at the site of the shooting.

Some held candles and signs that said: “What a tragedy, what a travesty.”

Friends and family have described the boy as a well-liked eighth-grader who played the trumpet and basketball and had a good sense of humour.