Sandra Bland was the one who hanged herself in jail. She couldn't make a very moderate bail, and her family didn't help her. Even if her arrest were improper - of which I've seen no proof - there is no way the relevant police officers could foresee that she would commit suicide. As for 24-hour surveillance of prisoners, run that idea by the ACLU before posting something so silly.
Philando Castile was pulled over because he resembled one of the perps in a recently reported robbery. While Castile supposedly informed the officer that he had a gun, as he moved his hand toward his right leg and hip (disobeying the officer's instruction after he said he had a gun), the gun was visible, near his hand, and the officer shot him.
Ramarley Graham was in a residence the police had been surveiling, and entered that evening to make arrests. The officer encountered Graham in a hallway and instructed Graham to show his hands. Instead, Graham ducked into his bathroom, and when the officer next saw him, he appeared to be reaching into his waistband.
Eric Garner was selling cigarettes illegally, and the police attempted to arrest him. Garner resisted, and his heart and respiratory system couldn't sustain the strain of his struggling.
Oscar Grant and another person were being arrested by BART (Bay Area Rapid Transit) police after a fight on a BART Train. Grant resisted the officers, and after saying he was going to tase Grant, the officer drew and fired his gun. The officer was convicted of involuntary manslaughter, and found not guilty of second degree murder and voluntary manslaughter. On one hand, the meme MrS posted left out a lot of relevant facts; on the other, one of those relevant facts, the officer's conviction, seems to me to have been correct, based on what the prosecution could prove.
The Gregg Gunn case happened just this past March, and the officer has been charged with murder. Apparently Gunn was walking home at night in his neighborhood when the officer stopped him. A struggle between Gunn and the officer ensued which lasted for the length of a block - in which Gunn evidently used a metal painter's pole he had been carrying and the officer tased him - and the officer shot Gunn. The officer reported that he did so when Gunn took a position in preparation to attack him.
So, yeah, the meme MrS posted leaves out so many relevant facts that it is nothing more than a lie crafted to deceive. "oberliner" pointed out that the same designed deceit was true of another person cited by MrS's meme.