Graphic video images of Tuesday's shooting of Alton Sterling, 37, unleashed protests and social media outcry over alleged police brutality against African-Americans.
Then on Wednesday night Philando Castile was shot by US police after being pulled over while driving in the Minnesota town of Falcon Heights, just outside Minneapolis.
Castile's girlfriend livestreamed the bloody aftermath in a video viewed by some two million people.
We look at similar cases that have rocked the US in the past few years.