Largest gator in the Western Hemisphere?

I got an email from a friend recently, to my great disappointment the pictures did not load but the beast description did. The so called "alligator" was found in New Orleans and measured 21 feet and weighed 4500 pounds! To me this sounds a little fishy and also put to credit it was an internet story and the pics in the email did not load.

The brief description went on to describe that the army killed it because they thought it would be a problem, and do to its "age" it would be to lazy to hunt animals, and it would target humans. So they killed it without proof. Don't get me wrong this guy, if he is or was real, would probably have become a problem. But they didn't have to kill him, captivity could have been an option. Look at Gomek for those who have heard of him. 17 foot saltwater crocodile became a problem croc but was put into captivity at the St. Augustine Alligator Farm, and he lived the rest of his days happy and fed. He even tamed down and seemed to settle into his new life.

So you can see why I would be pissed if this supposed giant was killed without proof of a murderous streak, assuming he existed at all. If you have any information please let me know, I would like to see this colossus if he is real.