I think my son had the worst experience I've ever heard of.
He was camping at high elevation in the national forest of Utah. He took a hike, and met a couple and three kids while hiking in. While fishing, a terrible lightning storm came up, so he took shelter as best he could. As soon as the storm passed, he hiked back to the parking area. Both of the adults that he'd met were laying near the parking lot and had been fatally injured by a lightning strike. All three of the kids were injured. He used his cell phone to call for help, and after the authorities arrived, he returned to camp very shaken up.
Earlier, before he went fishing, the couple in the campsite about 50 yards away had been arguing, but he didn't think anything of it. When he returned to camp, the woman had been shot to death and the husband was gone. He raced back down to where the authorities were taking care of the lightning victims. Dozens of law enforcement personnel arrived around the campground to investigate the crime scene. Unfortunately, my son had his family with him, and although he tried to protect the children from seeing anything, they still understood enough to be traumatized. The whole family needed some counseling after these events, and they were pretty anxious during their next few camping trips.
They can all joke about it now as the recall the camping trip from hell, but that's an experience I never want to endure.