It's a breakdown of the incident with many different angles!
You can hear Rosenbaum say: let's get their guns (paraphrased)
Also you can see that Rosenbaum actually tied his shirt to his face before he was chasing Kayle Rittenhouse.
Why would he suddenly mask himself? Because he had the intention of severely harming Kayle?
Check out this video: https://www.youtube.com/watch?v=KNGsixl34MI
It's a breakdown of the incident with many different angles! You can hear Rosenbaum say: let's get their guns (paraphrased) Also you can see that Rosenbaum actually tied his shirt to his face before he was chasing Kayle Rittenhouse. Why would he suddenly mask himself? Because he had the intention of severely harming Kayle?