Compare hairline of this guy with the inside the chamber one of grey hair guy on left.
In both pics, guy has earpiece in his right ear.
Inside chamber view (ymani cricket post):
https://freerepublic.com/focus/chat/3921491/posts?page=4186#4186
Shooting video still (#1pal post):
https://freerepublic.com/focus/chat/3921491/posts?page=4346#4346
My observation:
Earpieces are different; shooters one has a small wand mike.
I don’t think the USSS uses those.