Mark of the Lash by Chet Cunningham
Matt Hawk charged north from San Diego to get away from a murderous drug cartel. He and Brandy, his ward, landed in Portland, Oregon but he immediately gets involved in a hunt for area militants after one of the outfits tried to gun him down. He and a Portland cop work to find the militia outfit that has stolen medical radio active material from a hospital and threaten to explode it over the Portland Rose parade and kill hundreds. The race is on to see if Mark can stop Tony Carlton and his deadly gang in time to save the parade and the lives of hundreds.