What do you do when your 15 year old son

[KinseyWinsey]

Tells you to go fuck yourseff?

Remove his phone, pc, until he can apologise and act appropriately

What do you do when he's built like a brick shit house and merely smashes things up when you take action?

Ask him who the fuck he thinks he's speaking to!
After that, I'm guessing it's been said in anger or frustration?
Let him cool off and explain that you will not be spoken to like that again. He is out of order and disrespectful and if it does happen again then loss of his privileges, that you pay for, will occur. See it through.

Is it out of character? does he have issues expressing his feelings normally? Has anything changed recently that he is worried about?
Are a few things I'd question.

Oh then you have a bigger issue than swearing

Once he is calm you will have to sit him down and explain why he can't act like that, also make him pay for any damages he causes.

With your update I’d phone the police. Unacceptable. Is there an underlying issue with him?

Is there a father? I would suggest even if you aren't together he needs to step up and support you. Social services is your other port of call for advice, if you feel in danger call the police. You are not alone

I don't know, it has never happened with either of them, nothing remotely like it in fact, and I hope it never would. Unhelpful but you did ask.

More helpfully, agree with PP that it doesn't sound like this has come out of the blue and he has form for aggression, verbal and physical. If it has gone this far I think you do need to seek outside support and help, possibly via the authorities, as your relationship aside, he is not legally allowed to threaten you never mind cause you harm.

With the physical violence I'd have him arrested, son or not.

Sorry I commented just after you'd updated OP
Yep if he's being aggressive and damaging property etc..
Then you need external help.

@KinseyWinsey

What do you do when he's built like a brick shit house and merely smashes things up when you take action?

Police

Can you speak to the school? Counselor or head of year?

I think it’s really difficult to say as it really depends on what came before. How he has been raised in terms of how he can speak to you? What consequences are standard for the household? Any additional needs/past traumas/mitigating circumstances?

Context is everything.

Why focus on the swearing rather than the da heroics criminal violence? In the case of the latter you obviously phone the police because you and anyone else in the house is at serious risk.

Hi there does he have any other underlying issues or problems? You could try googling Young Minds for their help, also look up the anger iceberg image. Anger is often the outward presentation of a host of internal problems.
Are you getting regular breaks from each other? Sometimes you need a bit of distance from each other to cool down, get some perspective and put plans or consequences into place. Is there anyone at school who could help?
Good luck to you I know this can be exhausting, infuriating, frustrating and heart-breaking all at the same time.

I am not sure, really and your situation is serious.

With my teen boys I always work the angle that I am a person, and like all people I deserve respect. My biggest weapon is telling them they hurt my feelings. I tend to walk away from them when they are really arsey.

You don't give a lot of detail, but you also might try and "mood match", by which I mean stay calm, reasonable, and don't engage with anger. Like you would with an angry 3 year old, you can address the issues without letting your emotions add to the anger or chaos in the room. He is feeling very emotional and if you feed it by matching anger it will all grow even more chaotic. It is hard to rage at someone who is calm.

@KinseyWinsey

What do you do when he's built like a brick shit house and merely smashes things up when you take action?

Call the police and have him arrested

Tough one. Contact the school/ children's services, tell them you cannot cope. He is violent physically and verbally and that if he doesn't leave you will kick him out ( I know that's extreme but it's your safety at risk here)

You can't deal with this on your own, OP. It's dangerous. I think you need to call the police immediately you become threatened. Is his dad around? Is there anyone in the family who he respects?

Get his dad or another male authority figure to put him in his place.

Call the police, give him the shock of his life, if he carries on the way he is he'll likely end up in prison.

Depends whether you feel he could be a danger to you or another family member. Police if so - they won't necessarily arrest him but would calm the situation and make onward emergency referrals to social care.

If it's bluster, keep at a distance and allow things to calm down. At 15 you could leave the home for a short while unless you think he is at risk of serious self harm or causing significant damage.

If you think its mental health related, you can call an ambulance.

Is there a history of this sort of behaviour?

You need to find out the reason for it. Is this a recent thing or has he always been like it?

Son or not, with any violence i'd call the police without a doubt.

Context is relevant. Does he have SEN? Is this a recent change to behaviour.

It would be terrifying if a 15 year old boy acted liked this as assume he is almost adult side. Calling the police would be the last resort and if he was in danger or putting others at risk and could not be reasoned with.