Watching here in Denver. There are definitely at least two groups. During the day, it's people with signs and chanting and in general peaceful protests. But then there is a smaller group that is just interested in chaos. Before the tear gas started, the leaders of the peaceful protests recognized what was going to happen, and then started telling people that if they were there for peaceful protests to head toward the steps of the City Hall building (which is a huge terraced area) and then go home. The Twitter videos show the peaceful protests trying to get the chaos group to leave, stand down, don't deface the statues and buildings, etc. They ignored and started throwing bottles and things at the the police. Unfortunately, once the tear gas started it overcame both groups.
EDIT: So even a Denver Council member is saying that, after 15 hours of being there, he agrees with the observations that it is white anarchists "creating mayhem" and that black people are going to get blamed for it.