My best friend.
When we were freshmen in high school (2003), I woke up one morning to hear the phone ringing. My mom answered it, then a moment later, she came bursting into my bedroom, wailing and screaming "Sara died! Sara died!" Horrible way, by the way, to inform someone that their best friend was dead, but obviously my mom was panicking and not thinking straight.
The night before, Sara had been hanging out with another one of our friends when she suddenly had a seizure. As far as I know, she was never prone to them before (we'd been friends for three years and no one had mentioned any health concerns aside from a food allergy). The friend performed CPR while her mom called an ambulance. When the paramedics showed up, they used the defibrillators on Sara multiple times, but her heart had stopped and wasn't starting again. She was fifteen years old when she died.
Aside from the whole obvious "mourning the tragic and premature death of my dearest friend" thing, my life was very strange for a while afterward. The more polite kids would stare at me in the hallways, the more bold ones would ask me if I was present when she died and ask for gruesome details. Teachers that I previously hadn't gotten along with suddenly were extremely invested in my well-being, giving me hugs without asking and telling me they were available to talk if I needed it. My stepmother, who is a psychotherapist, began psychoanalyzing me on a daily basis without permission, and I got a flood of sympathy cards from my religious fanatic relatives telling me that her death was "part of God's plan."
This was nearly 12 years ago. I've healed just fine, no remnants of psychological trauma or anything. I miss her, of course, and every year on the day of her death, my mom goes to the cemetery in my stead (I live out of state now) and leaves flowers on her grave for me. I... don't really know what else to say, if anyone has any questions I'm happy to answer them.