I guess the above poster is thinking of the shoot-to-kill era of the 80s (still well within living memory): https://en.wikipedia.org/wiki/Shoot-to-kill_policy_in_Northe...
The political situation in the late 1960s provided plenty of kindling, but it seems clear that most of the sparks that actually caused the conflagration came from the barrel of guns held by soldiers and the police. They were directly responsible both for the death of the civil rights movement and the collapse of the government, and without the heavy-handed response it's likely that the settlement of the late 90s would've happened 25 years earlier.
It's actually a great example of why the militarisation of policing should be resisted at all cost.