When you and your brother were herding the buffalos, one of them escaped. You went to get it back and while you were gone some bad people came after your mother and your brother. Of course you are completely devastated and you want to get revenge on the people who did this. Try to find them to make them pay for what they did!
To move use WASD, to draw your gun or put it back in its holster use J, to cock or shoot your gun use K and to interact or confirm use E.