The police shooting of a man in Louisiana has added to concerns about excessive force used by police against mostly black victims.

Alton Sterling's death was filmed on the mobile phone of onlooker and activist Arthur Reed, who was just metres away as two white police officers tried to arrest the 37-year-old.

Mr Sterling, a father of five who had been arrested a number of times before, had been selling CDs outside a Baton Rouge convenience store.

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Police say they had been sent to the store at 12.35am on Tuesday after an anonymous caller told them that Mr Sterling had threatened someone with a gun.


Image: People in Baton Rouge have been protesting against the shooting

In the phone footage, the two officers pinned Mr Sterling to the ground, someone yelled "He's got a gun! Gun!" before gunfire erupted.

According to the area's coroner, Dr William Clark, Mr Sterling died from multiple bullet wounds to his chest and back.

Baton Rouge Police Chief Carl Dabadie Jr said that Mr Sterling had been armed but the circumstances which led to him being shot were still unclear.

He described the shooting as a "horrible tragedy", telling reporters: "Like you, there is a lot that we do not understand. And at this point, like you, I am demanding answers."

The two officers - Blane Salamoni, with four years' experience, and Howie Lake II with three years - have been placed on administrative leave, as is standard policy.

It is not known whether one or both fired their guns or how many times.

Baton Rouge Police said the officers had been wearing bodycams but that these had become dislodged during the scuffle.

Police said the cameras and other evidence - dashcam and shop CCTV - had been handed to the US Justice Department, which has started a civil rights investigation into the incident.

According to the owner of the convenience store, Abdullah Muflahi, Mr Sterling had been confused about why he was being arrested.

Mr Muflahi said he saw Mr Sterling being thrown on top of a car bonnet and he could hear him asking: "What did I do wrong?"

The 28-year-old store owner, who also recorded the shooting on his phone, said he never saw Mr Sterling with a gun but saw a police officer pull a gun out of Mr Sterling's pocket after the shooting.

Hundreds of people protested against the shooting on Tuesday night and into Wednesday, with Mr Sterling's family calling for the police chief to step down.

Edmond Jordan, a lawyer for Mr Sterling's family, said he "was not reaching for a weapon".

"He looks like a man that was actually fighting for his life."