There are all kinds of "buck fever", and many degrees of it. I've read about guys who levered all the bullets out of their rifle, thinking they were actually shooting at the deer - then couldn't figure out why the deer didn't go down. Fact was, all the unfired bullets lay beside them on the ground.
Usually, buck fever is merely the increasing of the heart rate because adrenelin is being pumped into the bloodstream due to the excitement of seeing a buck. Heck - even a doe, if a person thinks a buck may be nearby.
I have been deer hunting for over 35 years and have harvested many deer. Last week when a doe came into view about 75 yards away and I was scoping her out for antlers, I couldn't help but notice that my heart was beating rapidly even though I had been sitting for 2 hours!
Watch some of the TV hunting shows and you'll see that even the "pro's" usually are very excited after the shot. "Give me a minute to catch my breath!" "Oh, wow, that was great!" etc.
I'd say that what you experienced was normal. I've found it helpful to talk to myself a little at that time, take a deep breath (don't forget to let it out and keep breathing!), then concentrate on the spot you want to shoot - not on the antlers.
I guess if deer hunting ever ceases to excite me I'll quit (but I don't think it will happen)