We didn’t stipulate the track tying murderer was being executed, looks like they’re fighting on top of a train. There may not have been any options to stop them falling off the side.

And of course they’re dangerous, they tied a huge number of people to train tracks against their will. That implies a lot of strength, cunning and martial skill, and willingness to do harm up close and personal. Without overwhelming force the only way to neutralise a threat like that may be to kill.