Yeah, this happened with the shooting at the SLC protest earlier this year. A protestor with a gun was shot at by security, then accused of shooting the person who died. Open carry is allowed in Utah. Whether or not you think marching while openly carrying is a good idea. Unfortunately I understand the stress of the moment and it can be hard to figure out who is responsible while acting quickly.
https://www.utahpoliticalwatch.news/what-actually-happened-a...