Where did you got the MTA 0.5r2 ?
If you got it from Project-Redvivus then there should be a commands list on their wiki,
if you got it from here, the only command I know is /kill
well, you would need to use: colshapes:
createColRectangle
createColSphere
More here: Colshape
then when they enter it, use these functions:
setPedWeaponSlot
then use the event: onPedWeaponSwitch