(CNN) The grandmother of Stephon Clark, the young black man shot and killed by Sacramento Police last week, pleaded Monday in a passionate speech for justice for her grandson.

"They didn't have to kill him like that. They didn't have to shoot him that many times," Sequita Thompson said through tears.

"Why didn't you just shoot him in the arm, shoot him in the leg, send the dogs, send a Taser. Why? Why? Y'all didn't have to do that," she added.

The tearful plea came as part of a press conference with Benjamin Crump, an attorney representing the Clark family. Crump said the family is preparing for an independent autopsy of Clark's body.

"We will stand up for Stephon, we will speak for Stephon, we will fight for Stephon, until we get justice for Stephon," Crump said.

"I want justice for my baby. I want justice for Stephon Clark. Please, give us justice," Thompson said.

The press conference came a week after Clark, 22, was shot and killed in his grandmother's Sacramento backyard by officers who believed he was pointing a gun at them, according to police. No weapon was found at the scene. The only item discovered was a cell phone, police said.

Sacramento County Coroner Kim Gin determined Clark's cause of death was multiple gunshot wounds, with the manner of death being homicide. A spokesperson for the coroner's office said the exact number of gunshots that hit Clark is not being released at this time. The full autopsy report will be held until the case is adjudicated in court.

Crump was retained by Clark's family late last week. He has previously represented the families of other African-Americans fatally shot by police, including Michael Brown and Tamir Rice , as well as Trayvon Martin, a Florida teenager killed by George Zimmerman.

Crump said Clark's death fits a pattern in America of police shootings of unarmed black and brown people.

"No family should have to endure this pain and suffering as they try to seek answers for an execution of their loved one who is only holding a cell phone," he said.

'Great mistrust'

On Sunday, Crump told CNN that police showed no "humanity" toward Clark after he had been shot.

"While he laid down on that ground dying, they waited six minutes. And then they go over to him after that and they put him in handcuffs," Crump said.

Crump also noted that shortly after that, police muted their body cameras

"Why didn't you try to help him?" the attorney asked.

Speaking on Sunday, Crump said Clark's death should not be "swept under the rug." Crump also called for accountability from both sides, and said he will be exploring "every legal remedy possible" in search of justice.

Stephon Clark with his two sons.

Sacramento Police released body camera video of the incident that also showed that the officers did not immediately provide Clark with lifesaving efforts, instead waiting until other units arrived at the scene.

"There's great mistrust" between communities of color and police, Crump said.

"The only way we can bridge this divide of mistrust is to have transparency and accountability," he said.

Two officers -- one of them black -- have been placed on paid administrative leave pending the outcome of a use of force investigation.

Body camera video captured the shooting

The shooting happened on March 18 after 9 p.m., when Sacramento officers responded to a report that a man had broken car windows and was hiding in a backyard. They pursued a man who hopped a fence and was in a backyard.

The shooting was captured by the two officers' body cameras and a police helicopter; that footage was released on Wednesday in an effort to be transparent.

The body camera videos show the brief encounter between police and Clark, lasting less than a minute.

Police said the officers entered the front yard and saw the suspect along the side of the home. The man "turned and advanced toward the officers while holding an object" extended in front of him, according to the police account.

"Show me your hands!" one of the officers yelled. "Gun, gun, gun."

Seconds later, officers opened fire as they took cover near a wall.

As more police arrived at the scene, someone is heard asking, "What did he have on him?"

An officer responded "... something in his hands. It looked like a gun from our perspective."

Clark's family has disputed the police account.

"This was an unnecessary killing of an unarmed black man yet again," Crump told CNN. "What we saw in that video was not reasonable well-trained officers."

Sequita Thompson recounts the horror of seeing her grandson, Stephon Clark, shot by police.

Police said they found at least three vehicles with damage they believe Clark caused, as well as an adjacent residence with a shattered sliding glass door. Deputies in the helicopter witnessed him shatter the door, police said.

Stevante Clark told HLN his brother "wasn't a thief."

The Rev. Al Sharpton , the prominent political activist, has pledged his support for Clark's family and said he would be in California to help them fight for justice, according to a statement from his organization.

CORRECTION: This story has been updated to correctly describe Benjamin Crump's past clients. An earlier version of this story also said Trayvon Martin was slain by police. He was killed by George Zimmerman.