Michael Arnette is correct.The neck is too long for a mountain lion but the neck and shoulder are consistent with deer.A mountain lion's neck is actually shorter than it's skull.
A mountain lion's ears are much wider at the bases and are black on the back.This even shows up with an IR flash.In the photo,you are seeing the back of the right ear and at the bottom,rear of the left ear,you should have also seen black.
Notice how the skull is arched up,between the eyes.All lions have this,not a dip between the eyes.A mature lion can have a crease down the top of the cranium,like a bear but that crease starts well behind the eyes.The eyes are also,proportionally too small for a lion.Lions have large eyes.
You can see the width of the ear base here.It is about the widest part of the ear.
It's a strange looking animal in the picture for sure.The ears have a more deer like shape but are unusually small.I guess that happens occasionally but that one's pretty unusual.Even dogs have ear bases similar to cats.
Whatever it is,I'm positive it isn't a lion.