Aggressive rabbit

I am house sitting and got a call from my mom, her male rabbit attacked her female. He bit her face, I couldn't understand my moms description of the wound. All I know is that there was a lot of blood and it is a large hole. She is currently driving roughly 2 hours to the closest emergency vet.
We've had problems with her male rabbit since getting him at 2 months old, hes now almost a year. He's shown some agression to us, but never anything serious. Shes been working on the slow bonding and it's gone well so far, until tonight. I wasnt there to monitor so I'm not sure how it all happened, and my mother was rightfully too upset to tell me the details. All I know for sure is he was making growling noises and lunged for her face. Now her female seems to be crying, bleeding and tried to bite my mother when she tried to grab her to calm her and examine it is all understandable. I'm sorry for this being so long, my point is:
Since he's shown agression for so long (he is neutered) and he is very anti social and just not friendly unless you're showering him with treats and even then he will get angry fast. Do any of you have tips to help him? I'm sure my mom is furious with him and possibly thinking of getting rid of him out of anger. But I do not believe she will when she calms down, despite his behavior he is loved. My 4 year old brother calls him his baby and bestfriend. I just want to try everything I can to help him because I know if the behavior continues to get worse my mom will weigh the options more seriously.

A male rabbit (even neutered) being aggressive toward another rabbit doesn't necessarily mean that he is aggressive -- just that he doesn't like that particular rabbit. Not all rabbits will bond and I've had a few cases where two rabbits simply would not get along. One female I had rejected (viciously rejected) two male rabbits before finally liking a 3rd.

As for not being friendly, that is just the way some rabbits are. Treats will often make these types of rabbits temporarily overcome their inhibitions.

Is he lunging or nipping or biting anyone (human)? Or is he just avoiding attention?

His behavior has gotten worse since his neutering. It's a slow change but looking back on how he was months ago vs now it's like a whole new rabbit. He lunges at my feet when I go in to feed and change his water, I haven't taken it seriously until now. He scratches and bites at my feel and pant legs but again didnt really bother me until now. We've noticed it's not as gentle, the bites are getting harder and the scratches are leaving marks and if you dont wear socks they draw blood sometimes. He was litter trained, he actually didnt leave an random poops outside the box for months but now he almost never uses his box. He attacks the broom and dust pan when we go to sweep it up, he also digs/chews up the carpet now. We clean his pee off the floor and rug just for him to do it again. I know some rabbits are just difficult but he wasnt like this before, he is like a whole new rabbit. We have to take the injured rabbit to the vet for a procedure tomorrow morning and we will talk with them about this behavior change since they know how he was before hand.

Some rabbits can get "cage aggressive." From what you describe, it sounds like his "attacks" are when you are in his cage/territory? Adding food or water to his cage... sweeping up his poos in the cage... these "attacks" seem to be happening when his territory is being intruded upon.

If this is the case, he may be insecure and lashing out with this cage aggression. It is best to save cage cleaning to when he is not in his cage. Wait until he is out getting his exercise to sweep up. Be sure that food and water dishes are near the entrance to the cage to minimize your intrusion in the cage when filling (though still try to fill when he's distracted).

I like to consider a rabbit's cage his domain, his safe-zone, his area in which he will not be disturbed. I think some rabbits really need this kind of space more than other rabbits in order for them to feel not threatened. Perhaps changing your routine and allowing him that space may help him to settle down. It may take time and consistency for him to see that his space is truly his "safe zone." This may help him. It would also be a given, in this scenario, that he not be forced out of his cage nor forced back in. He can be coerced to go back in (with treats, for example). The idea would be that he thinks he is the one deciding to go back in.

Giving him control over his own little area/cage may do wonders to help him feel more secure. This would be my suggestion for starters. Hopefully, with enough consistency, this will help him improve. If not, then other options could be considered. But I'd start with this since it is easy enough to do.

He isn't a caged rabbit, he has a cage but rarely goes in it. He is kept in my mother's room will full access, it's been like that since about a 2 weeks after getting him at 8 weeks. It's only the last few months that the agression has gotten worse and we cant think of anything that has changed to cause this.

It is possible that he has some underlying health issue that is making him grumpy.

It is also possible that he sees the entire room as his territory and is upset now - as an adult - that his territory is constantly being intruded upon. The fact that he rarely goes in his actual cage would support this. (BTW, my rabbits are also free roam all day, every day, but are confined at night.) Rabbits are considered adult at around 6-7 months of age, so this seems to have started as he became an adult.

If this were my rabbit, I'd consider a do-over to get him to change his perception of what is his territory and what is shared territory. The only way to do this is something he isn't going to like but may be ultimately best for him and your mom. Confine him to his cage for two weeks. During that two weeks, attempt to 'neutralize' the rest of the room as much as possible. Wipe everything down with vinegar to remove scent. Re-arrange furniture. Do whatever it takes to make it seem as unfamiliar to him as possible. This will be key to this plan working.

After the 2 weeks, allow him out in a limited area around his cage (perhaps making use of an x-pen). The idea is to grant his freedom in controlled limited amounts. In his case, I would also suggest having several hours per day (or night) where he will still be confined back in his cage -- just to be sure he gets the message that the cage alone is his territory alone.

After he's had several days at least of making use of the new, limited area, then that can be expanded to the whole room. Again, still have several hours of confined cage time per day or night.

It may seem harsh to confine him, but it will do him no harm to be confined for these short periods of time (nor will it do harm to be confined for those first 2 weeks). Doing less than the 2 weeks will sabotage the goal. He'll need that time minimally to get the message.

Again, the ultimate goal is for him to change his perception of what is his territory. You want him to see the room as shared territory to eliminate his need to protect and defend it.

Completely agree with blue eyes that he probably thinks the whole room is his territory, follow the good advice given above