I have been watching this discussion, which is of interest although I am "over the pond" in the UK where civilian possession of an 'assault weapon' has been illegal for many years - after mass shootings - and we have no constitution too. Caveat aside now.

However in my reading I came across this, which adds a certain poignancy to the discussion:
Eden (Albuquerque police chief) showed a video of one protester – clad in body armor – armed with an AK-47 assault rifle. The man loaded the weapon and urged onlookers to “use force against the police officers,” Eden said....Police know the assault rifle was real because officers had seen it and a review of video of the man – who put the rifle back into a van after the crowd disapproved of his actions – confirmed it. The man disappeared into the crowd, Eden said, and was not arrested
There was another protester with an AK47.

To say the least there is a mass of context to this event within a protest over a mentally ill male being shot dead by the police. If interested the officers video is available:http://www.youtube.com/watch?v=JwytoxMuk4U#t=14

It does illustrate the dangers posed to US LE in such a situation, one where it is the police who are the target of the protest.

Link to local press report:http://www.abqjournal.com/377167/new...ame-a-mob.html

The BBC coverage of the protest:http://www.bbc.co.uk/news/world-us-canada-26814976