It's hard to say why the deer was in distress. Hopefully they were able to get it the help it needed or euthanize it humanely.
You have to be careful approaching, let alone picking up and handling, a deer or pronghorn (antelope). I heard a funny story about some guys near here many years ago who went out one evening to poach an antelope (technically a pronghorn). They shot it and loaded it into the trunk of their car. As they were driving, they heard a lot of noise from the trunk and when they stopped, they could see dents appearing upward in the trunk lid. So they got the good idea to have one of them open the trunk while another one would shoot the critter again. Unfortunately for them, they managed to shoot a hole right through, puncturing their gas tank.
That's one of those stories where they really got exactly what they deserved!
Critters like that can be stunned or sick but suddenly come to life with a burst of adrenaline when they feel threatened. I wouldn't want to be kicked by a deer. But it was nice of the animal control and police people to help the poor thing.
I like how your camera zoomed and followed the action well, even as the light transitioned between just enough for color to low enough to need to go to IR. Excellent!