how can i restart the mission at central union railroad

[R.I.P BOO]

i just started the game i didnt know how it worked and i had like 300 dollar bounty and i found that mission randomly and i started it and like mid way the bounty hunters came at me and i killed them and everyone in the camp also attacked me and then i came back later to try to do the mission and they all threaten me to leave and the percy dude says oh no not you again we dont want any trouble and then i get trespassing and i cant do the mission this is kinda cancer and if i have to restart a save thats like legit gona give me cancer