NEW : Mike McLelland asked about guns for his staff before his death . The FBI is investigating the shooting of a U.S. Border Patrol agent in Arizona and whether it was linked to an earlier incident involving two other agents who were killed last year. Miller is being held on $ 1,000,000 bail . Authorities say there is no connection between Miller and the killings .
NEW : Mike McLelland asked about guns for his staff before his death . Robert Alan Miller , 52 , of Terrell , Texas , is accused of threatening a prosecutor . Miller is being held on $ 1,000,000 bail . Authorities say there is no connection between Miller and the killings .