On Wednesday 6 July, 32-year-old Philando Castile was fatally shot by police after they pulled his car over in Falcon Heights, Minneapolis.
The horror of the incident was broadcast around the world with breathless immediacy, with Castile's girlfriend Diamond Reynolds recording the events immediately after the shooting on her smartphone, streaming her footage via Facebook Live.
The video depicts Castile gradually losing consciousness at the wheel of his car, blood soaking his shirt, while Reynolds maintained an impeccably calm running commentary of the events, eventually being removed from the vehicle. You can find the footage here, but it's a deeply distressing experience.
It appeared that Facebook had initially pulled the video from Reynolds' page, causing many to wonder if the social network had been put under pressure to hide the footage. It subsequently reappeared with a graphic content warning, with a spokesperson stating it was "down due to a technical glitch".
Facebook Live is yet to really define its major purposes: is it a news tool? How will inappropriate content be handled? When is content too graphic for wider consumption?
This is what Mark Zuckerberg has to say on Reynolds' video: