Everyone in and around DC knows it was Lt Mike Byrd. He has served on the protective detail of both McConnel and Pelosi.
https://www.rollcall.com/2019/02/27/capitol-police-weapon-left-unattended-in-capitol-bathroom-again/
Big, physically imposing, very well dressed, good natured guy. Easy to remember, hard to forget. Two google searches will reveal his name. He is a member of the new American "average IQ praetorian guard", not high speed, just PC, and just barley capable enough to fight non criminals.
After the House adjourned on Monday, Lt. Mike Byrd left his Glock 22 in a bathroom in the Capitol Visitor Center complex, according to sources familiar with the incident. Byrd is the commander of the House Chambers section of the Capitol Police and was on the job Tuesday and Wednesday.
Byrd addressed the incident at Tuesday morning’s officer roll call and, according to sources, told fellow officers that he “will be treated differently” because of his rank as a lieutenant. It was not clear what exactly the lieutenant meant by the comment.