The killing of two unarmed men by US police has caused violent protests and national soul-searching in the US, and global conversations online.
Michael Brown, 18, was unarmed when he was shot in Ferguson by police officer Darren Wilson in August this year.
Several witnesses claim Mr Brown had his hands up when he was shot eight times, and "hands up don't shoot' quickly became a statement synonymous with excessive force used by the police, racism and black rights.
Eric Garner, 43, died after he was placed in a chokehold by police who had approached him for selling single cigarettes in July. He complained that he was tired of being harassed before Officer Daniel Pantaleo reached around Mr Garner's neck. Video footage captures Mr Garner telling the police 10 times he could not breathe.
In both cases, despite evidence, and even video footage in the Garner case, US grand juries voted not to launch criminal investigations into the conduct of the officers.
In November, police also shot and killed 12-year-old Tamir Rice who was waving a toy gun in a playground.
The deaths have been a catalyst for local rights groups and sparked protests across the United States and beyond.
Many have taken to Twitter to express their heartbreak and rage. After the grand jury chose not to indict Mr Wilson, #blacklivesmatter trended as people shared their sense of betrayal and what they saw as a sickening lack of surprise at the decision.
After the grand jury's decision not to indict Mr Pantaleo this week, #blacklivesmatter trended again but so to did #crimingwhilewhite, in which white people wrote about the better treatment they receive from police.
The conversation was a response to people sharing about everyday racism with the #alivewhileblack hashtag.
At 13 I stole a car with my friends & drove it 2wks before we got busted. Only one charged was black. #CrimingWhileWhite — Cecily Kellogg (@Cecilyk) December 4, 2014
REMINDER: Not arrested or tear-gassed while armed, obstructing traffic and inciting violence #CrimingWhileWhite pic.twitter.com/q2dfNZRQmX — The Baxter Bean (@TheBaxterBean) December 4, 2014
When I was a young boy I brought a toy gun in my carry-on to the airport. Instead of shooting me, they mailed it home. #CrimingWhileWhite — David McDowell (@dgmcdowell) December 4, 2014
Going 75 in a 55. Told the cop I had a fight with my boyfriend. He let me go. #CrimingWhileWhite (Also true.) — Amanda Marcotte (@AmandaMarcotte) December 4, 2014
Incredible RT @Durags4Eva: RT @blowticious: #CrimingWhileWhite pic.twitter.com/6NBBr1nrs5 — NoMore Cheating.org (@__J_R) December 4, 2014
Shot 72 people and killed 12 in a movie theatre and was subdued and arrested unharmed. #CrimingWhileWhite pic.twitter.com/E10H7esPhF — Nate Ogborn (@nateog91) December 4, 2014
While many have welcomed greater awareness among white people, most agree discussing it on Twitter is far from the direct action so desperately needed.
#crimingwhilewhite doesn't help me. I already know what you get away with. You need to listen to what we die for. — Ijeoma Oluo (@IjeomaOluo) December 4, 2014
#CrimingWhileWhite is useful IF it enables wider debate & acknowledgement of our privilege, not so much if it becomes a trendy funny meme. — Peter Vincent (@PeterVthatsme) December 4, 2014
BREAKING NEWS: Police are upset about the #CrimingWhileWhite trend on social media, but they've decided to let everyone off with a warning. — Chris Rock (@ozchrisrock) December 4, 2014
Maybe sharing light-hearted stories of how good you've got it isn't the best way to show solidarity w/ grieving people? #CrimingWhileWhite — Andy Richter (@AndyRichter) December 4, 2014
Folks, I understand the INTENT of #CrimingWhileWhite. It's as evident as white people's urge to make everything about them. — Andy Richter (@AndyRichter) December 4, 2014
The #alivewhileblack hashtag makes for even more powerful reading.
I was stopped 29 times by cops in E. Europe during my 18 months as a Fulbright Scholar. Police racism is a world issue. #alivewhileblack — Terrell J. Starr (@Russian_Starr) December 4, 2014
dad got arrested for "breaking" into his own home, and when given proof that it was his house, they still arrested him. #alivewhileblack — simi (@bx3__) December 4, 2014
When you want to travel abroad and the first question you ask yourself is "Do they like black people there?" #alivewhileblack — Janelle James (@janellejcomic) December 4, 2014
I got pulled over, cop said he pulled me over for "looking like" I was about to start speeding. Car was on cruise control. #AliveWhileBlack — Alexis (@MusicOverPeople) December 4, 2014
Crossing the grocery store parking lot. Cops stopped to ask me what I was doing there. I was holding grocery bags. #Alivewhileblack — Mikki Kendall (@Karnythia) December 4, 2014