Blaming demons for evil acts is the most common in organized religions.
Partially not true. Demons will come to anyone unless anyone does malevolent intentions in his/her heart.
Let's say that Rob bullies Jon every single day and killed him at school. Not a single facility member of school boards willing to investigate the situation and let it slide.
Days go by Rob continues to bullies another person at school. One day Rob heard a voice and it keeps bothering throughout his school years. He started acting weird toward his parents and his friends. None of them can understand his craziness. His friends ditched him. His parents bring him to doctors and they can't find anything unusual about his behavior. Not even a Pastor or priest can't exorcise the demon.
The demon was bound onto Rob for the rest of his miserable life. Whatever Rob feels afraid of anything or get angry all the time, the demon can enter his heart then his mind and take control every aspect of him. When the demon take control, it'll attack his family or anyone. This is where Rob end up in the Asylum and no one will ever come to see him again. Rob cannot eat or drink whereas the demon is in control. Weeks go by the Rob's body slowly wither. When his body dies, his soul travel not in aerial dimension, but in pitch darkness where the demons await him and dragging him to hell.
For those who haven't done anything malicious acts but died from some sort of accident or died from old age may wonder will end up in somewhat dimension. Staying in that dimension too long has a downside for lost souls. Demons will do anything to distract them and lure them in the front door of hell.