It only happens once a year and only lasts a moment, so catching this on camera is monumentally lucky. If you are worried that this was painful for the moose, don’t be. The National Geographic had this to say about the process:
“Moose and other deer relatives shed their antlers every year, and the process is thought to be painless. Usually both antlers are shed within hours or days of one another. Bulls will occasionally try to speed up completion of the process by knocking the old antlers against trees to shed them.”
If you ever get to see this in person, recognize you witnessed something very few people ever will. Very very cool.