The human "turning off (the agent)" could be substituted with "removing a necessary resource to complete the specified task". Say the electricity, either of the agent, or even just the coffee machine.
Sounds like an OSHA violation, but not a new or different one. You can already get run over by a forklift if you're standing in front of it. There's various things we do about that, but they're boring real-life things, not fun logic-puzzle things, so they're just not mentioned in the problem. There isn't a way to categorically prevent machines from accidentally killing people though.