Grumpy Double Yellow-headed Amazon?

by Jimmy Reed
(Delphi, IN, USA)

Hello! I have a question. About 2 years ago. My mother received a Double Yellow-Headed Amazon parrot from a co-worker of hers. He now belongs to us... But... Ever since we've had him he has been a total grump. He is approximately 10 years old now.
Our parrot will not let us touch him. Occasionally he'll let me touch his beak, then he'll lash out and try to bite me again. Most people can't even get close to him without him lashing out and trying to bite.
I have thought, maybe it was the people who had him before didn't train him well? If that's the case is there a way to reverse what they have done to him. Is there a way to make him friendly again or will our parrot be a grump for the rest of his life.

I very much love our bird and I'd like to be able to pet him, but with the way he's acting it's almost impossible to do so.

Any advice you guys can give me would be greatly appreciated. Thank you for your time reading things, I look forward to anything you'll have to say!

Thank you!