Sec. 3. Be it further enacted, That every person who shall willfully run any horse or fire any gun or pistol within said corporation, shall for the first offence, pay the sum of five dollars, and for the second offence, shall pay ten dollars, and double that for any other offence, to be recovered before the President of the Selectmen of said town; Provided, That no person shall be liable to the penalties for shooting, when the same may be accidental or necessary.