I'm guessing you're from Europe, because what you call Deer, the USA call Caribou or Elk, and what we call Deer aren't nearly that big.
Male deer with antlers routinely gore dogs where I’m from. Deer, not elk.
Or he has seen Disney movies and thinks caribous are male deers.
Elk and caribou/reindeer are both kinds of deer (so are moose for that matter... for him to speak of 1000 lb deer, he must be thinking of moose or be mistaken.)
In the San Francisco Bay Area, our native California Mule deer that commonly roam suburban streets, weigh in between 100 and 300lbs.
White tailed deer on the east coast and midwest are in a similar size range.
And the little Key deer down in Florida, which are the smallest of the North American Whitetails, are typically about 40-50 pounds. One night when I was down in the Florida Keys, typing away at my laptop on the beech in the dark, I felt something cold and wet touch my elbow. I looked over my shoulder, and a little Key deer was sniffing my arm. I jumped a bit, and then the deer jumped a bit, and with one last curious look, she ran off into the dark. Very cute little thing.
What deer are these? Deer in my area rarely weigh over 200 pounds.