Well, back in the day (1200-1400's, somewhere), in some parts of Europe, the hangmen/executioners were actually often criminals who got to choose between being executed themselves or kill as a profession. Kill or be killed, so to speak.
In this case we have a guy who is forced to do it, and at the last moment he refuses. Therefor, he himself gets executed.
And yes. There is some irony in it. The video producers are quite fond of these kinds of twists...
I could not keep my hands off that, of course. ;)
/The Black Knight