TEMPE, Ariz. (AP) — An Arizona prosecutor said the man arrested in the shooting of a Democratic National Committee office in suburban Phoenix had more than 200 guns and over 250,000 rounds of ammunition in his home, leading law enforcement to believe he may have been planning a mass casualty event. Maricopa County prosecutor Neha Bhatia said at Jeffrey Michael Kelly’s initial court appearance on Wednesday that federal agents told her about the…