It was probably close to 13 years ago, I can't recall exact what content. Based on where I was in my life, I'd say it was free to air TV. We selected the channel/content but didn't have a smart TV yet (it may have been a few DVDs).

I remember thinking at the time it was benign content, but also wasn't so aware of what to look for. The worst content was probably the Teletubbies.

I put it down to amount of time in front of a screen & exposure to rapidly changing images.

The angry, violent behaviour disappeared soon after removing the TV.