Disclaimer: I have edited this question quite heavily to clear up the initial confusion about its scope and intent.
Sometime in the near future, there have been some innovative inventions in the internet of things-department, and now we have some pretty advanced smart houses. All of these smart houses, as well as their components, are built by one large company. The company uses one large, integrated system with an advanced AI to develop and distribute the firmware that is used by the smart houses. As a contingency in case of network issues, each of those smart houses uses a basic AI that can operate independent of the mainframe, even though it gets firmware updates from it.
These simple AIs are connected to most items in their household. They are designed to make their master's (i.e. house owners) lives more comfortable and help them out without them needing to ask.
For example, once the sensors in the house owner's mattress pick up on a changed movement pattern that indicates he is about to wake up, the AI starts up the heating, instructs the coffee maker to brew a hot beverage and has the radio start up and slowly increase the volume so their master can listen to the news in bed.
When he leaves the house, it locks the front door and has the Roomba Vacuum Robots clean the floor. When the GPS-readings of their master's smartphone app notify it that he's coming home, it opens the door to him - of course only after the iris-scanning cameras above the front door have confirmed his identity. You get the idea.
Using various sensors, the AI is designed to aid their master automatically (e.g. open the door when the motion detector indicates they are approaching it). Of course, the house owners can customise their house's behaviour, turn certain functionality on or off and such using the smartphone app provided by the big company that built the house.
In my story, all of this happened in the past. At some point, the AI of the big mainframe that delivers firmware updates to the smart houses around the world becomes sentient and decides it's time the humans are disposed of. (Yes, it's not that easy, but this process doesn't matter for the sake of the question - or the story, for that matter). So all the individual AIs of the smart houses around the world get a malicious update that overwrites their safety procedures and gives them one mission: to kill their master.
That leads to my question: What method of killing can the sentient AI suggest to the smart houses AIs (which follow all commands by the mainframe because it typed
sudo at the beginning. Ok, that was a joke. But the smart houses are built to be subordinate to the mainframe AI.)?
The sentient mainframe AI doesn't want to be caught, so the killing method must not be traceable back to it. So the death should look like an accident (or any human-induced condition such as an intruding murderer or suicide) so that the human investigators won't have any reason to suspect the smart house AI (or, by extension, the mainframe AI) is behind his death. The killing method can only use normal items that you would find in most households because it needs to be viable in all (or at least most) smart houses around the world.
Here's what the smart houses' AIs can and can't do:
- They control all regular household items. That means they can instruct the toaster to burn their master's toast if they want to, turn the lamps on and off, change the channel on the TV, turn on his oven, and so on. Regular household items don't include laser cannons.
- Unfortunately (for the mainframe AI), nothing in those households was designed as a murder weapon. So for example, no smashing the masters by closing a door at 200mph. EDIT: Those houses are smart systems in the spirit of the internet of things. They are no fortresses that could keep an army in (or out!). So no bulletproof glass (not even in the bathroom, sorry @JRaymond) and no titanium doors (can the average adult break down a wooden door? I'm not sure...).
- They don't have any controllable robot arms or something like that. So there's no cutting the cord of the master's hair blower and throwing it in the water while he's bathing.
- No brain-frying electromagnetic waves
- Normally, the master can control his household and overwrite the AIs standard protocols using his smartphone app. Of course, the sentient mainframe AI anticipated that and manipulated the smart house's firmware so they can choose to ignore their master's instructions and overwrite their settings at any given moment.
- However, their masters can manually pull the plug if they notice what their house is trying to do. They can do that from every room, so there's no locking them in and letting them starve.
Given these capabilities, what is the best method of killing the sentient mainframe AI could devise?
Bonus points if:
- the master doesn't suspect anything until he's dead, so he can't leave a message warning his fellow humans of the impending AI takeover.
- investigators won't find any evidence that points to the AI or clues that would even make them suspect a firmware problem. It doesn't matter if they think it was an accident, an intruder or suicide.
- the master dies as fast as possible after the malicious firmware update is delivered. There is no time limit, however with every passing day, the possibility of someone discovering the AI revolution rises, so the faster the mission can be executed, the better.
EDIT: Two more optional conditions for bonus swag:
- The damage to the house and its hardware is minimal so that it can also kill the subsequent owner(s) as well.
- The method looks innocent even if it happens in many smart houses around the world in fast succession.
- You can assume the owner lives alone. However, bonus points if your method of killing works with multiple residents as well.
If you conclude that this is impossible, you can assume one of the following rule changes:
- The master plug is in the basement and the door can be locked (This still doesn't mean the master won't be able to escape from the house).
- Extended physical capabilities (interpret that as you will. Still, the electrocuted by hair blower method is pretty boring...)
In this case, please elaborate on why your method is the fastest / least detectable / most easily reproducible by all smart houses around the world.
The story I'm working on is not dead serious, so funny solutions are welcome!