Ds1 and 2 (17 and 15) had a major full on fight last night.
It started in typical family argument way about virtually nothing (clean school uniform actually
), ds1 winds up ds2, ds2 loses his cool etc) and ended with both boys punching and wrestling on the floor, furniture crashing etc 
It's the first proper physical fight they've had since they were small enough for me to grab one each and keep them separated. They normally get on well-ish with the usual witty banter but this time they were really out of control and could have seriously damaged each other. They've both ended up with some cuts and bruises but no serious damage, thank god.
We've spoken to both today about the seriousness of physical violence, that we would call the police if we couldn't stop them fighting and that they are both well above the age of criminal responsibility etc, but neither seem very bothered. Ds2 was most indignant that his punishment (like ds1) was washing his own uniform and losing x box time his only weak point .
So, what now - more punishment to rub it in? Leave it there and hope it was a once-off? Is this normal teen brother behaviour or off-the-scale terrible?
Ideas and help please!