Another possibility is that the shooter is someone related to a case that Booth and Bones are currently working on. This person could be trying to stop them from uncovering the truth and will go to extreme lengths, like shooting Booth, to keep their secrets safe.
Maybe it's a rival agent who is jealous of Booth's success and popularity within the agency. They might see shooting Booth as a way to get ahead in their career or gain more power within the organization.
One possible plot could be that Booth is shot during an undercover operation. Bones then uses her forensic skills to find the shooter. She might face many obstacles like false leads and interference from the criminal underworld. Meanwhile, Booth is in a critical condition in the hospital, and the team is rallying around to support Bones as she tries to solve the case and also deal with her emotions for Booth.
It could be a jealous rival detective who wants to get rid of Sherlock to gain more fame in the detective world.
It could be a dark wizard who has a vendetta against Fairy Tail. Maybe someone who Natsu defeated in the past and is now seeking revenge.
It could be a new villain who has a vendetta against Tony. Maybe this villain has some past connection to Tony that we don't know about yet, and they finally take their chance to harm him by shooting him.
It could be a former criminal that McGee helped put away. They might have escaped from prison and are seeking revenge on him for ruining their life.
There's also a possibility that it's someone who has a wrong idea about Conan. For example, a person who thinks Conan is involved in some sort of conspiracy against them or their family. This misunderstanding could lead them to shoot Conan in a moment of rage or fear, without really knowing who Conan truly is and what he stands for.
There's also a possibility that it's an agent of a secret organization. This organization might be aiming to disrupt the hero society, and they see Bakugou as a key figure to target. So they send one of their best shooters to take him down.
It could be a new villain, someone who has a personal vendetta against Peter Parker. Maybe a criminal whose operations Spider - Man has disrupted one too many times.
Maybe a mysterious figure who has some connection to the shooting, either as the shooter or someone who has some prior knowledge about it. This character could add an element of mystery and intrigue to the fanfiction as the other characters try to figure out their role in the whole situation.
It could be Nathan Prescott. He has a history of being unstable and involved in some dark things in the game. Maybe he has finally snapped completely and decides to target Max for some reason, perhaps because he feels she's getting in the way of his family's plans or because he blames her for his own problems. Another possibility is that it could be someone from the other side of the Arcadia Bay conflict, like a person who doesn't want the lighthouse to be saved and sees Max as the main obstacle to their plans.