The hardcover debut of paperback hero J.P. Beaumont, a Seattle homicide cop who, here, is called to the massacre of Officer Ben Weston, his wife, two of his kids, and a playmate, with the sole eyewitness being the officer's five-year-old son. While forensics is working through the apartment, J.P., standing at the front door, is nearly killed by a drive-by shooter. Is it open season on cops? In any event, J.P. is soon at odds with the murder task force and troubled by what looks like rogue cop involvement. He and a rookie female cop, plus a wheelchair-bound former homicide cop now assigned to media control, eventually alert Internal Affairs, participate in meetings of local teenage gang leaders, and, thanks to a computer whiz, resurrect the dead cop's computer homework--all of which will lead them to a mechanic in the police car pool and to a pair of bad cops on the take. Unpretentious journeyman stuff, but, in its quiet professional way, solid entertainment for police procedural fans. J.P. (another A.A.-er) is a genial, decent guy to root for.