Way, way back in the day when dial-up was a thing, I worked at a company that had an automated system that called a large bank of test numbers to make sure they were still working. This system ran 24/7. It required you to put in the numbers as <areacode>-<number> without a prefixed 1. The code would add the 1 automatically. Because it operated in a lab inside of our phone system, it dialed 9 to dial out. Well, at some point someone had to reconfigure this system and I guess thought it would be good to add a 1 before each # in the configuration.
This resulted in thousands of 911 calls being made to our local call center. We had accidentally created a 911 war-dialer.
The moral of this story is don't dial 9 to get an external line. You're literally a keystroke away from calling 911 every single day.