Perhaps a mysterious stranger who has some unknown vendetta against the Heartland family. This person could have been lurking around the ranch for a while, waiting for the perfect opportunity to strike. Or it could be someone within the community who has a hidden agenda and sees Amy as an obstacle to their plans.
Maybe it's a human who has somehow discovered the world of demigods and is afraid of their existence. They shoot Annabeth out of fear and misunderstanding. Another option is that it's a rogue demigod who has gone bad and is working against their own kind. This character could have a personal grudge against Annabeth specifically, perhaps because of her intelligence and leadership skills which they envy.
Unfortunately, I don't have information on the author of this particular fanfic. It could be an amateur writer who just wanted to explore this scenario with the character Ciel. There are numerous fanfic communities where such works are published, but without more details, it's impossible to say who wrote it.
Well, without reading it specifically, it could be about a character named Ciel getting a shot. Maybe it's a medical shot in a hospital setting and the story focuses on Ciel's fear or bravery during the process.
In many 'Katniss gets shot' fanfictions, she might face a life - threatening situation. Her friends could rush to her aid. For example, Peeta might use his skills to protect her further while waiting for medical help. Maybe Gale tries to find the source of the shooter and avenge her.
In Pulp Fiction, the person who gets shot in the car could be any of the numerous characters involved in the complex web of events. It might be a result of a sudden turn of events or a long-standing feud. Without a specific memory of that scene, it's difficult to give a definite answer.
One possible plot development could be that his friends and family rally around him. They might search desperately for the person who shot him. For example, if it was a case of mistaken identity, they could start to dig into Sam's recent activities to find any leads. Maybe they discover that Sam was unknowingly involved in something dangerous, like being in the wrong place at the wrong time during a criminal deal. This could lead to a whole new sub - plot where they try to figure out who the real target was.