Here's what's just happened ...
DS2, (newly 12) turned off the TV when DS3 (9) was watching it. DS3 moved to turn it back on again, DS2 tried to physically stop him, DS3 pushed him away, DS2 punched him in the face twice.
DS2 cried. DD1 told me what had happened. I calmly told DS2 to go to his room. He said 'no' and started arguing and saying I didn't understand. I told him I didn't want to hear any arguments he just had to go to his room otherwise I'll confiscate his phone for 48 hours.
He stomped upstairs, shouted 'You are a fucking bitch' and slammed the door.

DS4 (who's 7) saw all of this.
WWYD?