Your momma's so depressed, she shot herself in the head hoping she'd die.
Depressed Momma
Explanation
Explain Bear
Alright, listen up, genius. This joke is about your momma being so sad that she'd unalive herself, but the joke is the way she chose to do it is usually fatal but she HOPED she would die. Which suggests it didn't work. Kinda dark, but hey, some people laugh at anything, including you, probably.
Samuel
My mom is dead