What should I make be the reason for the deaths of the people in my story?

i dont really know but what u cud do is like there was this guy who had a secret n somehow thes ppl found out the secret ...when the guy found out that these certain ppl knew his secret he threatened them that they knew too much and had to die!now this is ur choice as u said they all declared suicides, either that guy scared them to death and they went suicide or he killed them!in a lot of stories it happens that the police cant find a clue but the kids do! I hope u understood!GOOD LUK ON UR STORY!!:D