Do the dog, yourself and anyone who might come in contact with him a favor and have him put down.
I had a beautiful German Shepherd, male but neutered who thought the sun rose and set with me. He was 120lbs and one day had a seizure. I saw him leaning against the house with his eyes looking sort of glazed and slapped my leg while saying, Bear, heel. He knocked me down and went for my throat and face and only didn't seriously injure me because I put my hand down his throat. All the time, calling his name. Suddenly it was over and he was frantic because I was hurt.
It took only seconds but in those seconds he could have killed someone, would have killed a child. After the attack, he was gentle as a lamb again, but I had no choice but to have him put down. Rescue or a pound would have put other people at risk, and I couldn't bear the thought of him being abused.
OMG..that sounds like an utterly horrible and frightening experience.
And I'm sure putting down and old friend, couldn't have been a cake walk. But I completely understandable.
How sad.
Has anybody trained growling and aggression out of a dog?