Military members are considered "equipment," by the US military. The terminology originated with them. The thugs with badges are using it for their cosplay.
I can understand that when taken at face value. The reason for it is that as a member of the military, you are extremely technically no longer a citizen of the US, nor are you governed by the laws and regulations of the US. You are now governed by the UCMJ, which, in theory, is much stricter about what codes of conduct will be allowed in your day to day life.
To be even more fair, that is exactly the terminology used for military personnel medical procedures. We all know that the thugs with badges absolutely love to cosplay as military, so it follows that they would use military terminology.