The 22-year-old was shot at least seven times in his grandparents’ back garden after police were called to reports of a man smashing car windows.
Initial reports did not say Mr Clark could be armed, but officers opened fire after mistaking his phone for a gun.
The Sacramento county district attorney, Anne Marie Schubert, said the officers did not commit a crime and were justified in using lethal force.
The decision prompted angry protests in California‘s capital.
Black Lives Matter demonstrators marched down the streets of one of Sacramento’s most affluent neighbourhoods on Monday.
Police ordered the protesters to disperse around 9pm, but the Los Angeles Times reports that they had blocked the demonstrators’ path back to their cars.
After the marchers moved down the only path available to them, police followed and made arrests for unlawful assembly.
Although the Sacramento county district attorney said her office would not be filing criminal charges against the two officers, they could still be prosecuted.
State attorney general Xavier Bacerra is conducting an independent investigation into Mr Clark’s death and could supersede Ms Scubert’s judgement and file charges.