Sentence:  Rumors of the offer Tom Horn had made at the Stockgrowers' Association meeting had leaked out by then , and as a grand jury investigation of the murder got underway , the <WSD>prosecuting</WSD> attorney , a Colonel Baird , ordered that the tall stock detective be summoned for questioning . 
Meaning of the word marked with <WSD> tags:  a government official who conducts criminal prosecutions on behalf of the state