What was this weird material mask on a baby's face for?

Today I was out and I saw a baby ( no older than 8 months) with a cover over its head. It was shaped all the way around her head with slits for her eyes and nose and mouth. It was made out of a material that looked almost like a stretchy knee brace you slide up your leg to your knee. I've tried googling baby casts for face injures, or shaping the head and it is definitely not a head shaper. It was actually pretty scary looking, like something a murderer would wear, and my boyfriend and I have never seen anything like that before.

Thanks for the help!