What's the worst conceivable school shooting? If it was the last one.
Do you think school shootings are funny?
NO  School shootings are a plague that needs to be eradicated.
School shootings are traumatizing events for both the children and the parents and it can be triggering to even talk to them about much less joke about. Making light about it can be hurtful, just like you would be hurt if people made a joke about something that caused you pain.