Why do you think Dally chooses to die by this manner of death in The Outsiders?
There is a special relationship between Johnny Cade and Dallas Winston in The Outsiders. No one else is really close to Dally besides Johnny, and Dally has no close ties to the other boys. Consequently, Johnny regards Dally as a kind of chivalric character, much like the Southern gentlemen in Gone with the Wind. Dally lives much of his life on the edge, and Johnny's death is what sends him past the breaking point. He no longer has a reason to live with Johnny gone, and the pain of Johnny's death causes him to choose an unusual way out. By robbing the store and waving an empty gun at the pursuing police, Dally decides that his death will be symbolic of his troubled past and long juvenile record: suicide by cop.