Fine, raise the age to buy weapons to 21 BUT do you think mental cases like this will be any LESS nuts two years later? With luck, they would have been knocked off by cops before 21, but crazy is crazy at any age. Label them, restrict them, protect society.
The liberals regarded it as an act of kindness to empty the insane asylums and dump severely psychotic people onto the streets of our cities.
Perhaps its time consider reopening these facilities and get these people into a safer space with adequate treatment?