Why did the headphones my iPhone X screech and shut down my phone?

I was watching YouTube videos on my new iPhone X and when I closed out of the app my apple earbuds made a screeching noise and my phone shut down. This has only happened once so far so I’m not too concerned and it is probably some bug but I thought I probably should let you know since I was using apple headphones and an apple phone so it wasn’t a 3rd party problem.