So first off, that’s all absolutely horrible and I’m sorry to hear so many people you know saw such horrible things. My father was also a firefighter and he’d see a fair amount of things, things that changed him. Once, a woman who was only about a year older than I was at the time had had her 18th birthday where she was gifted a motorcycle. She decided to go riding around at night on the backroads and a deer jumped out in front of her. She stopped abruptly and went flying, landing on top of a railing which bisected her. She proceeded to bleed to death during the night, and was called in during the morning. He was one of the first on the scene.
My best friend (also a firefighter) was the first to respond to a car crash featuring a mutual childhood friend. He had seen him just 30 minutes prior at a Tractor Supply Co. Said when he got the call he had a sick feeling and rushed out to the scene. Found him unconscious, nearly dead, but still had a pulse. Not having the tools on hand in his car he did his best but ultimately had to wait for the firetruck to arrive, which by that time he said he had already passed. The ambulance said he died on the way to the hospital, but they tend to say that.
A family friend who’s a paramedic was haunted for decades by his first major call as a FR. He went out to a burning fireworks factory which had exploded shortly before he arrived. People were running out of the building on fire, screaming in blind agony as he watched helplessly. He was in shock and said for years he would close his eyes and all he could see was that. From what I heard he was always a bit distant after that, even by the time I knew him when he had (mostly) conquered it.