The boy that lived.
I personally have split, cracked, or broken atleast 3 helmets from falls, but had never seriously been injured. I had always been a huge helmet advacate because of horror stories I had heard about or seen end results, but never had a 'what if' story.
I was working with my first therapy lesson when the horse tripped and went down on both knees the little boy slid off toward the fence and under the horse before I could grab his foot. As the horse stood, he steped striaght back onto the little boys head and imeadtly reared up spinning around once he realized something was very wrong. The little boy lay screaming on the ground as I yelled for the volunteers to call 911.
Long story short, he ended up with a very deep laceration from ear to throat on his neck just under his jaw, a broken collar bone, but no head trauma. It was my first and only bad acident as an instructor and I was tramautized myself and even more so once I saw the damage to the helmet. It had a perfect hoof print pressed into the side through the plastic and indented on the inside of the helmet.
Had I given in and let him ride with no helmet as they sometimes did that boy would have been dead. After that I enacted the: if I'm working there better be a helmet on your head rule. After i quit one of the boarders was riding bare back down the busy road and fell from horse. She thanked me for making her put on her helmet before I left there wasn't much left of it after it hit the pavement.