Why are my cats suddenly attacking one another?

I have three cats. Bobbie (8 year old female), Lee J (7 year old male), and Bella (4 year old female). They have all lived together, with only the occasional spat, for four years now. Then, the other day they discovered a mouse in the basement that they all were stalking. None of them caught it (it went into a trap that we had set up), but a violent fight occurred over this (that I did not witness, but heard). We calmed them down with some food, but after wards Bobbie went tearing after Lee J, hissing and batting at him, while he ran scared. I went and found him, and picked him up to comfort him, when Bella came in the room and started violently attacking me (biting leading to blood and bruises) trying to get to Lee J. We separated them, putting Bella and Bobbie in a room, and Lee J in another for the night. For the next two days they acted fine with each other, but then at night we woke up to another fight of the two female cats against my male. We separated them again for the night, but then in the morning when we let them out, Bobbie started sniffing around, found Lee J's scent, tracked him to his hiding spot, and started to violently attack him. He is currently removed from the situation (my mom is going to take care of him for a little while and have my dad [a vet] look at him). This has never happened before. My cats have always been peaceful and have gotten along with each other (in fact, Lee J is Bobbie's biological son). All of them are spayed and neutered. But, it is strange that the female cats are not fighting with each other, only attacking my male cat. Even my dad is perplexed why they suddenly turned on one another. Has anyone had a similar situation, or can shed some light on the subject? I love my cats very much, and I want us all to be a family again soon.