Media playback is unsupported on your device Media caption Police say they thought Stephon Clark had a gun - he was holding a phone

California police have released footage showing the fatal shooting of an unarmed man whose phone was apparently mistaken by officers for a gun.

Authorities said they thought Stephon Clark, 22, had a weapon when they shot at him about 20 times on Sunday night.

Sacramento police said a man was seen breaking into at least three vehicles and a neighbour's home.

Bodycam and helicopter footage do not clearly show what Mr Clark was doing before he was shot in his own backyard.

It is dark in the clip, but a figure is seen hopping over a fence and running into a backyard.

Police officers' body cameras show them running along the side of a house to confront the suspect.

Image copyright Facebook / CBS Image caption Stephon Clark had two children under the age of three

Two officers who shot Mr Clark are purportedly heard asking him to show his hands and shouting, "gun, gun, gun", before opening fire.

Police said the suspect approached the officers with an object extended in front of him, which they thought was a handgun.

Footage from the helicopter shows Mr Clark collapsing as officers begin to fire, according to the Sacramento Bee.

One officer suggested disarming him with a non-lethal weapon, but stopped his thought mid-sentence, according to the footage.

"Let's hit him a couple of times with that before we uh...," he is purportedly heard saying.

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"What'd he have on him?" one of the officers asked.

"Something in his hands, it looked like a gun from our perspective," an officer responded.

Police approached Mr Clark and a mobile phone can be seen lying near his head. He is handcuffed by the officers.

While discussing whether to perform CPR, one officer said: "Hey, mute". The audio went silent for two minutes.

Mr Clark was pronounced dead at the scene.

His name was not officially released but his fiancee, Salena Manni, identified him. He had two sons, aged one and three.

The shooting has reignited the debate about interactions between law enforcement and African Americans.

The Black Lives Matter Sacramento group issued a public statement calling the shooting a "murder" by police after reviewing the video. They organised a public event in his honour on Thursday.

"He was at the wrong place at the wrong time in his own backyard?" Mr Clark's grandmother, Sequita Thompson, asked the Sacramento Bee newspaper.

The videos were first shown to the family before they were released to the public.

Police training expert Ed Obayashi told the newspaper that the officers' actions were "reasonable".

"It looks bad, but (the officers) are still perceiving a threat... he's not obeying," said Mr Obayashi.

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"The problem is he's got an object in his hand which unfortunately even during daylight could easily be considered a gun."

Ms Thompson, who heard the gunfire, said that she never heard police ask her grandson what he was holding.

Sacramento Mayor Darrell Steinberg said the investigation needs to be completed before he could draw any conclusions.

"Based on the videos alone, I cannot second guess the split-second decisions of our officers and I'm not going to do that," the mayor said in an statement to US media.