That’s a walk away and tackle later kind of problem. If their only move is “gun” then they have no other ability to protect themself. Walk away slowly, wait for them to let their guard down before tackling them in the scooter and taking their gun away. Let them cry that they can’t abuse anyone anymore. Point it at them to show them what it feels like to stare down the barrel of someone angry at you, uncertain of what the next few seconds bring.