Raptorzilla hatched out of his egg when the humans began building cities. This is what happened then.
Raptorzilla emerged from the ground and roared. He was newly born, but could walk, see, and was smaller than a person, like normal velociraptors. He took care of himself for three years, then was an adult, and could briefly fit a 5-foot tall man in his mouth. He traveled further than he ever did, and reached a city. He was confused when he saw everyone staring at him, then began rampaging and eating many people. He was thought to be a T-rex at first, but when the people saw how sleek and streamlined he was compared to one, they noticed it was a giant velociraptor that wasn't a kaiju, wasn't daikaiju-sized, but was still big and strong. He picked up a lady who freaked out, but then a man yelled, "Take me instead!" before Raptorzilla could eat her. He looked at the man, then dropped the lady, who ran away as soon as possible. Raptorzilla slowly approached the man then slowly opened his mouth, about to eat him. Before he could eat him, an army of men came with weapons and scared the oversized velociraptor off, and he began living in a thick jungle.