“In a 2021 interview with Lester Holt on NBC, Byrd said he could not see into the Speaker’s Lobby hallway through the glass, did not know if the person climbing into the window was male or female, and could not tell if the person had anything in their hands.”
In that case the logical thing to do is take the time for matters to make themselves clear.
With no immediate threat evident he had no justifiable cause to fire on the person crawling through the window.