Stephon Clarks heartbroken grandmother pleaded for justice Monday and announced plans for a private autopsy of her grandson shot dead by police as he held only a cell phone in her back yard.

Sequita Thompson broke down crying as she described hearing the boom, boom, boom, boom of 20 bullets unloaded in the dark of her Sacramento property shortly after 9 p.m. on March 18.

She described dropping to the ground in terror, crawling over to a 7-year-old granddaughter sleeping on a couch nearby and being told by detectives she shouldnt go outside to view Clarks lifeless body.

They didnt have to kill him like that. They didnt have to shoot him that many times, Thompson said through tears at a morning press conference in Sacramento with civil rights lawyer Ben Crump.

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Now my great-grandbabies dont have their daddy, she wailed.

Why didnt you shoot him in the arm? Shoot him in the legs? Send the dogs? Send the Taser? she asked, addressing the two unidentified Sacramento police officers who fired at Clark and are now on paid administrative leave.

I just want justice for my grandson, she cried. I want justice for my baby. I want justice for Stephon Clark. Please give us justice.

Crump said the independent autopsy is necessary to get answers on exactly how the hail of gunfire unfolded.

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They want to know exactly the points of entry. A lot of that will tell the story of what position he was in and whether they could have even imagined a threat, Rev. Al Sharpton told the Daily News on Monday.

Sharpton said he was asked to give the eulogy at Clarks funeral on Thursday, and he accepted.

All of it is disturbing to me, he said of the police response, highlighting how an officer at the scene said, Hey, mute, after the shooting, and then the sound on the body-worn cameras cut off.

Why would you kill the sound? The idea of having body cams is to vindicate yourself, Sharpton said. We need to deal with the facts. This keeps happening, mostly in black communities.

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The officers who fired on Clark claimed he advanced toward them holding an object they believed to be a gun.

No firearm was recovered from the scene, only the cell phone, police confirmed.

The officers were responding to a 911 call about a man allegedly breaking into cars and shattering a window of a South Sacramento home.

A crew member on a Sheriffs Department helicopter reported watching Clark pick up a tool bar before he allegedly broke a window on a neighboring house and jumped a fence into his grandmothers yard.

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Authorities said after Clarks death that investigators identified three vehicles in the area with damage they attributed to Clark. Investigators also reported finding a shattered sliding glass door at the adjacent residence.

Police did not report finding a tool bar near the broken glass door, only a cinder block and a piece of aluminum possibly used for a rain gutter installation, The Sacramento Bee reported.

Authorities released the helicopter and body camera footage last week as they acknowledged the seriousness of the situation and vowed an investigation.