Why do i keep thinking about evil since i saw a cloudly thing when i was young in my closet?

i keep thinking evil and devilish things i have night mares of people shooting them selves in the head and im not crazy i chekked whit a psychologist im a normal guy i graduated i did everything can some one please help is it because i was a gang banger when i was young i started be in a er when i saw that cloudy thing im serious i am not crazy they tested me for everything