I suspect they were under orders not to use deadly force and thus badly out manned. Take those in front out with single shot to center mass. Drop a few and the riot will go away. If it does not go away, “Cry Havoc and let slip the dogs of War.” Full auto will stop the riot.
I'm not disagreeing with that or the possibility that they were ordered to retreat. What galls me is that we work hard to have homes and families, only to see people entrusted to protect us cut and run, or those above them ordering them to cut and run at the first sign of trouble, leaving us to deal with the howling mob. If they can't, or won't, take their responsibilities seriously then QUIT dammit, and make room for those who WILL do their duty when things get tough.