A couple of questions :

Is Romeo neutered and what was the neuter / entire status of Max and the female [ you did`nt give her name, sorry to sound impersonal there ! ] ?

I ask that in case there are relevent dynamics as to why the problem was always with Max and only Max.

You say he often got through blockades to get to max - unfortunately something called Barrier Frustration only serves to increase a problem which sounds like exactly what happeneded here [ bearing in mind I can only go by what you have written ].

Was he ever kept separate from the female ?

I`m strongly inclined toward the initial problem being either direct hormonal cause [ if any of the three are / were entire ], or mental maturity kicking in given the age at which Romeo started having an issue with Max.

I`m not inclined to believe it was a deliberate out and out kill either, as he discontinued the attack, [ which was not actually witnessed anyway ], and was more likely just very unlucky and tragic that the jugular was caught, which can and does happen to some dogs even during clumsy play let alone in a fight I do think a lot of the reaction is based purely on his breed but all dogs have teeth and all dogs could cause this sort of injury whether intentional or not.

I feel that, had sensible crating been used rather than baricades which he had easily breached in the past, things may well not have escalated to this point or at least would have been far more easily managed and a tragedy avoided but hindsight of course is something which does`nt help right now

I certainly would not agree with those reacting with a death sentence when a good crate would solve a future potential indoor risk, [ and he has`nt been aggressive in any way to the female anyway - presumably no sign of a problem whatsoever between them throughout the two years of very clear persistant problem between Romeo and Max ? ], and a muzzle for walks is an easy enough option - why kill a dog when a crate for alone-time and a muzzle when sensible would prevent a problem which may well never happen again anyway and would at least give breathing space from making a knee-jerk decision right now ?

When you say he has never shown any other aggression apart from toward Max, I`m assuming you mean he has always been perfectly ok with other dogs on walks ? [ and its rare for any dog to always be perfectly ok with every dog they meet regardless of breed / size / age / gender ! ].
If not, again, an occasional muzzle usage is a perfectly reasonable alternative at the moment to death for a dog who sounds perfectly nice the rest of the time !

Is there no way he can live with you to take the pressure and heartache off your parents ? I know you say your apartment is too small but realistically, a dog can only take up its own bodyspace in one place at a time and I`ll bet your `small` apartment is likely to be far larger than typical UK flats / apartments
Physical room / space of a building really is not so much an issue as the quality of the life given to the animal/s within the home.

If you can take him home with you, you know him very well, you know the problem he had with Max and that it was limited aggression, [ as in not to any other dog and not to people ], but if you can`t, a good sized crate at your parents for times he would be unnattended with the female would be a sensible basic start.

Getting in a good behaviourist whiotruly understands aggresion issues, [ not one who thinks all dogs should be dominated and certainly none who use violent / pain / fear methods ], would be a very good move as any aggression really is best dealt with one to one by someone knowledgeable, outside of the situation, who is able to read dogs signals well, can read the interactions within the home between the dog and their human family as well as other animals present, and would be able to give a much clearer assessment than we can here without seeing him ourselves, and can help with any relevent health tests which may be pertinent [ especially thyroid panel which I feel is a check far too infrequently considered yet which is a primary cause of so many aggression issues either regardless of, or combined with, any other health or life experience causes as well as neuter status of all dogs involved in dog aggression cases ].

Which ever way you decide to go, I do feel for you all at the loss of Max, and for the uncertainty and confusion you must all be feeling - and the confusion / anxiety which Romeo may have been feeling for the last couple of years.

I do hope you are able to take some time, [ utilising any sensible safety precautions as anyone would do ], to find a resolution from which you and Romeo can move forward.

Thats your choice Sara, I dont shut dogs in crates, I do use them when a puppy is tiny, as I think they can be excellent for house training, and I also use one when the dog is on a show bench, but I dont use them if I am out, nor do I shut dogs in them all night. I dont have a problem with them at all, however my point was that some people think shutting a dog in a crate is the answer to every problem, not their use in daily life.
Dawn.

What I dont agree with is people saying it will/could be a human next - a dog aggressive dog is a very different thing to a human aggressive dog and Im surprised some people are not aware of this

Patch, not that I would disagree with you but crating a Pit Bull that wants to kill something wouldnt be the best idea in the world, either for that dog or the ones it wanted to get at. I dont believe in shutting dogs in crates, for some folk they are the answer to everything. I agree that we can only go on what we have been told, and the dog is dead now, poor thing.
Dawn.