Lovey Senior Cat, Neutered for 16 Years, Gets Violent

My beautiful long-haired cat is a love-bug. But today for the 3rd time, he attacted me, and hard, and would not stop. I have a question and hope for some advice.

He was about 1 and neutered when we adopted him. He's always been sensitive to people. If someone is feeling a little sad or sick, he will offer lots of love. He kisses me. Indoor only. 16-year loving home with 2 very kind adults.

First time he attacked, I was brushing him. This was last year so he was about 16. I hit a mat by accident. He leaned back, got angry eyes, and lunged. He wrapped his arm around mine, clawing and biting. He drew blood and bruised me. I screamed and he moved.

Next couple of times, I saw him for no reason start to get angry eyes. I moved.

Today out of the blue, he purred cutely til I picked him up. He began to snuggle. Then he bit my hand hard. I screamed and got him off me. It was hard to make him move. He jumped back and clawed and bit which drew blood and left a bruise.

He kept trying to get me again, over and over, with those same angry eyes. I had to throw a robe over him to stop him.

Now he's all purry and cute and happy.

What should I do? What can make this happen? He had a full veterinary exam in January.

Are there drugs that can help?

He's so extra special - the most beautiful and smart cat we've ever had. Now I'm scared of him. I was on the phone with a business and suddenly I'm bloody and screaming! I don't know what set him off!

All thoughts are welcome and thank you.