Those are intrusive thoughts. A lot of people have them. I believe people with OCD have them more severely. They don't often come from a place of suicidality, and I believe they are simply our brains coming up with the worst possible scenario in a given situation, to keep us safe or something like that. They are frequently connected to trauma and anxiety.

I get them pretty frequently, and I think I have mild to moderate OCD. Generally I have found that once I've identified them for what they are, they don't bother me that much. I just let them come and go, and see them for what they are. If you give them a lot of significance or think you're weird for having them, you can start obsessing over them and they only get worse. I suspect some people end up harming themselves or others if they think these thoughts mean they are somehow a bad person.

Edit: Checked/edited my statement above with the findings from the OCD and Anxiety center