At first, the militia mob was prepared for Pence to reject Election Outcome by US Military. They were there to protect Pence to do his job from some other protesters.
But once Trump and US Military had realized Pence would do his standard job according to the Constitution, they had prepared to hang Pence. US Military ordered their military and militia agents to start shouting “Hang Pence!”. Then US Military ordered those military agents to enter in order to get Pence so that they can hang him.
A guy with red checkers shirt constructed gallows to hang Pence and probably other Democrats like Nancy Pelosi.