Not usually. Most two-sentence horror stories are products of the authors' imagination to create a creepy effect.
Most of the time, no. They're often crafted to shock and scare, drawing from common fears and creative ideas rather than real events. But sometimes, they might be inspired by real-life situations in a loose way.
Generally, they aren't. Two-sentence horror stories are typically fictional creations aimed at giving you a quick jolt of terror through inventive concepts rather than being rooted in actual happenings.