Both utterly shameful, and completely predictable.

Protesters called Friday for federal authorities or a special prosecutor to investigate the fatal shooting of an unarmed man by a Chicago police officer after Cook County State's Attorney Anita Alvarez announced earlier in the week that she would not bring charges in the case.

Prosecutors announced Tuesday that their two-year investigation into the shooting found that Officer Gildardo Sierra had reason to believe his life was endangered when he shot 16 rounds at Flint Farmer in June 2011. They contend the evidence supports Sierra's assertion that he mistook a cellphone in Farmer's hand for a gun and acted in self-defense.

Farmer's father, Emmett, joining protesters who carried photographs of his son holding a puppy and chanted for Alvarez to resign, said he wants federal investigators or a special prosecutor to review the evidence.

"The video shows Sierra standing over my son and firing three shots into his back. What else does she need?" Farmer declared as he and more than two dozen protesters rallied outside the county administrative office in the Loop.

Farmer's death marked Sierra's third shooting — the second fatal one — in six months. Police Superintendent Garry McCarthy told the Tribune that he considered the shooting a "big problem" and acknowledged the department had erred by allowing Sierra back on the street given the previous shootings.

The city later settled a lawsuit brought by Farmer's estate for $4.1 million. Sierra, 33, has been assigned to desk duty since the Farmer shooting.

A video of the shooting shows Sierra fired his final three shots into Farmer's back as he lay on the ground. An autopsy by the Cook County medical examiner's office determined those were the fatal wounds.

Prosecutors, however, contend the video offered only a partial glimpse into what happened after Sierra responded to a 911 call in which Farmer's girlfriend reported he had badly beaten her and her child.

Sierra told investigators that Farmer was pointing an object at him when he opened fire — an assertion prosecutors say is backed up by the location of a bullet wound on Farmer's right hand.