The family of Stephon Clark, an unarmed man shot and killed by Sacramento police last week, plans to file a wrongful death suit against police, the family’s attorney told The Daily Beast.

Clark’s family has retained Ben Crump, a civil rights attorney who previously represented the families of Trayvon Martin and Michael Brown. Like Martin and Brown, the 22-year-old Clark was an unarmed black man whose shooting death sparked national outcry. But the investigation into Clark’s case is just beginning, Crump said.

“They’re devastated,” Crump told The Daily Beast of Clark’s family on Monday. “It’s hard for his grandma to believe he was killed right behind her bedroom window.”

Police body camera and helicopter footage revealed that two officers pursued Clark through his Sacramento neighborhood, after receiving a 911 call about a man breaking into cars. When Clark stopped behind his grandmother’s house where he was living, the officers ordered him to put his hands up. The officers immediately shouted that Clark had a gun, and fired 20 shots at him, killing him on the spot. Police later stated that they believed Clark had been holding a weapon or a toolbar, but that he had actually been holding a cell phone.

Clark left behind a young family, including his girlfriend and their two sons, ages one and three.

The family is suspicious of the official narrative, Crump said.

“They feel that, at best, police have intentionally misled them, and at worst they flat-out lied to justify this execution of Stephon Clark in his backyard,” he said. “[Police] said the first day after the execution that he had a weapon, that’s why they had to shoot him 20 times. Then the next day they changed it and said he had some kind of crow bar or toolbar, to justify why they had to shoot him 20 times. Then finally they came clean and said he didn’t have any weapon of any sort. All he had was a cell phone.”

“ They feel that, at best, police have intentionally misled them, and at worst they flat-out lied to justify this execution of Stephon Clark in his backyard ” — Attorney Ben Crump

Part of the family’s suspicion stems from body camera footage released by Sacramento police. Minutes after the shooting, an officer is heard telling telling another to mute his body camera. The footage shows officers standing and talking, but the audio is missing.

“The family feels it’s very suspicious. They feel that, right before that, there was a profane word used,” Crump said. In one of the body camera videos, and officer mutters “fuck” after other officers arrive on the scene and start discussing the shooting.

Clark’s family thinks police “realized they had messed up. That it was a bad shoot, and that at that point somebody — [the family] think it’s a superior — told them to mute their mics so they could try to conspire and get their story right.”

Crump stopped short of calling the officers’ actions illegal, but said Clark’s family plans to conduct an independent autopsy and announce a wrongful death lawsuit on Monday.

“What we want is transparency and accountability,” he said. “We want to make sure the powers that be will hold police accountable, just as if this matter was reversed and it was Stephon Clark who had shot them. All the family wants is equal justice. They want due process for Stephon Clark.”

Crump said Clark’s killing is the latest instance of local law enforcement disproportionately targeting black men and boys.

“Take Sacramento, for instance: over the last two years, of all the people shot by police, over 85 percent were African American men,” Crump said. “Sacramento doesn’t have that great of a black population. So why when they use deadly force, is it mostly against African American men?”

Clark’s March 18 death has set off protests in his hometown and across the country.

“The wheels of progress turn slow,” Crump said. “We just have to try to believe what Martin Luther King said: the moral arc of the universe is long, but we have to believe it bends toward justice.”