The year is 2100. Internet 3.0 has arrived, with an ubiquitous Internet of Things. Even your wedding band has a fingerprint scanner to make sure it doesn't get stolen. An evil AI has been developed and is determined to kill everyone; however, people are still active enough that it can't make any preparations for the first assault or they would notice. It must use what it has.
For the first assault, therefore, it has decided to crash and/or disable all means of transportation, burn all buildings, and disable all electronic communication. To ignite the homes, it decided to short out or overload the batteries on all electronic devices. Assuming each home has 3 or more such devices and 99% of personal computing devices (cellphones, laptops, and desktops) and servers successfully ignite in a 6 hour time frame, what happens to the city?
The fire department cannot get to the scene (remember, their truck either won't start or was smashed into a tree/building/whatever), the phone system is down (there is no centralized system that can take control until after the 6-hour period is over--if then), and other events are wounding and killing people rapidly. Additionally, the water supply has been shut down, along with the rest of the computer-controlled infrastructure. Essentially, any firefighting efforts are by individual people. In a city the same size as 2018 Chicago with 90% of the buildings 30 years old or less and built with 2018 building materials, techniques, and codes, what would the result of such an action be?
Would fires even start? If they did, would people be able to put the fires out as they started, or would the fire take hold? I know a single home would burn to the ground, but would about skyscrapers and commercial buildings? Would it burn a single room out, or would the whole building burn down? Would it be able to spread to other buildings as it would in the suburbs, or would it remain localized to one building?