By Sonya Hamasaki and Dan Simon, CNN

(CNN) -- The family of Stephon Clark, an unarmed black man who was shot and killed in his grandmother's backyard by Sacramento police last year, has filed a wrongful death lawsuit against the officers involved and the city of Sacramento.

The federal lawsuit, filed Monday, alleges the 22-year-old was racially profiled, and the officers used excessive force in the shooting incident. The two officers failed to identify themselves or issue a verbal warning before firing approximately 20 shots, the suit said. The lawsuit also alleges the officers did not get him medical attention immediately after the shooting.

The Sacramento Police Department has never publicly identified the officers.

Clark was struck seven times, including three times in the back, according to an autopsy released by the Sacramento County Coroner's office. An independent autopsy found that Clark was shot eight times, six of those wounds in his back, according a forensic pathologist retained by Clark's family.

Authorities have said the two Sacramento officers who shot Clark were responding to a report that a man had broken car windows and was hiding in a backyard. Police chased that man -- later identified as Clark -- who hopped a fence into his grandmother's property. He was shot in her backyard on the night of March 18.

Police said the officers who fired at Clark believed he was pointing a gun at them. But investigators determined Clark was actually carrying a cell phone.

"When the facts are fully disclosed, we are confident that a jury will deliver justice that reflects how grossly the police land city officials failed Stephon, his family and the people of Sacramento," Brian Panish an attorney for Clark's children said in a statement.

The lawsuit, filed on behalf of Clark's sons, his parents and grandparents, seeks damages of more than $20 million, plus funeral and burial expenses.

"The Sacramento police executed Stephon Clark in his grandparents' backyard, mistaking his cell phone for a gun, assuming he was a criminal threat simply because he was a black man," civil rights attorney Benjamin Crump, one of the attorneys representing Clark's family, said in a statement. "Stephon's life had value. In America, a life -- even a black life -- can't be arbitrarily extinguished without holding those responsible accountable."

Sacramento police had no immediate comment on the lawsuit. When reached by local media, including the Sacramento Bee, the department referred questions to the city attorney's office.

"Out of deference to the judicial process and because this is a matter of active litigation, we must respectfully decline to comment," City Attorney Susana Alcala Wood said in a statement.

The officers' union could not be reached Monday.

The Sacramento District Attorney's Office is reviewing whether the officers' conduct constitutes a crime that could be prosecuted under state law, the office said in a statement. The California Attorney General's Office previously said it was also conducting an independent investigation.

In October, the district attorney's office said it received "the voluminous investigative report and related materials" about the shooting from Sacramento police.

On January 16, the district attorney's office said prosecutors also received "substantial investigative reports and related materials" from Department of Justice investigators in the Attorney General's Office.

"Our timeline for completion of our review has thus been delayed as we process the supplemental materials. We will take whatever time is needed to ensure a fair, thorough, and accurate review of this matter," the statement said.

After the shooting, protests erupted for several days in Sacramento as tempers flared. Frustrated residents and Black Lives Matter activists urged accountability for the shooting. At one point, protesters blocked the entrance to the Golden 1 Center, where the Sacramento Kings play, forcing them to play a game against the Atlanta Hawks in a nearly empty arena.