I'm not sure specifically about his role in 'Police Story' without more research. But generally, he might have played a police officer or a character related to the police operations in the story.
Since Erik Estrada starred in 'Police Story', his performance was likely a significant part of what made the movie appealing. He may have used his physicality to great effect, perhaps in chase scenes or in confrontations. His facial expressions and line delivery would have helped to convey the character's thoughts and feelings. Moreover, his interaction with other actors in the movie would have created the relationships and tensions necessary for a good police - themed story. If he played a police officer, he might have shown the different aspects of the job, like the stress, the loyalty to the badge, and the relationships with the community.
In the 'the lyle and erik menendez story', Lyle and Erik Menendez are brothers. They are known for their heinous act of killing their parents. Their case got a lot of media attention and raised many questions about family and crime.
Since it's a fanfiction, Erik Lehsner could be an original character created by the author. He might be a fictional being with certain special traits or powers that are important to the story. Maybe he's a supernatural entity, like a vampire or a wizard, which would add an interesting dynamic to his relationship with a human.
Erik is likely not based on a true story. Many such characters are invented to entertain or convey certain themes and messages, rather than being rooted in actual happenings.
It can start with conflict. Raoul is the 'good guy' and Erik is seen as the 'bad guy' at first. But as the story progresses, they could find common ground. For example, their shared love for Christine could be the starting point. They could have a conversation where they both admit their feelings for her and realize that they don't have to be enemies.
In fanfiction, Erik's possessiveness of Charles might be an exaggeration of his character trait. He may have a sense of ownership over Charles due to their shared experiences, like founding the X - Men together. His possessive nature could also be a way to show his intense love or loyalty towards Charles, in a rather extreme way. He might think that Charles belongs with him more than with anyone else, whether it's in their mutant - related activities or in their personal relationship.