https://www.politifact.com/article/2021/apr/20/update-capitol-police-officer-sicknick-died-natura/
Aside from suffering 2 strokes, the autopsy found no evidence of reaction to chemical agents, and NO (none, zero, zip, Nada) signs of any injury. I'm not a Dr., but I think being hit in the head with a fire extinguisher would leave a mark.
And does the name Seth Rich ring a bell??