We're going to have to agree to disagree LostDragonflyWings.
I disagree 100% with your advice and with the Cesar Millan method of training.
I think "correcting" aka "punishing" a growling dog is ASKING for the dog to escalate the behavior. I didn't say to let the dog just growl away. But dogs do not try to "dominate" people. Growling = Fear, NOT dominance. And if you think that's how dogs work than we are not going to agree on much. I'm done with this discussion, glad what works for you works, but I hope you don't get bitten one day.
My dogs do not fear me, I have never "corrected" them, bumped them, manhandled them, yelled at them, or even raised my voice, EVER, and they are two wonderfully behaved dogs. And they didn't start out that way, they were a wreck. One grew up feral and the other is a wolf hybrid. I also work with dogs as a living. But it's okay, we don't all have to agree! :)
Cesar Millan bullies dogs into shutting down. That's why they don't react. But do you know what happens after a dog shuts down? Fallout. No warning, no way to know it's about to happen, and BAM, someone is bitten.
If you need any evidence it's all here in this video. Cesar doesn't understand dogs, has no qualifications other than being on tv, and is just a bully. Dog Whisperer: Showdown with Holly - YouTube
My advice to the OP was already given. And after seeing her recent post, between everything going on, especially the heartworms, I think the dog should be euthanized. The heartworms are going to kill him anyway, to be honest. :( That is not to be taken lightly. Heartworms kill.
I'm not sure why a 15 year old is "fostering" dogs in a household where one member is afraid of dogs and she is away at school all day, but I'm not going to get into that.
I suggest the OP and anyone interested do some reading about calming signals. This dog probably showed quite a few before "suddenly" attacking.