The HOA Murders

Two old men who bullied their neighbors in a homeowner's association (HOA) are found shot dead in the Arizona desert near the Mexico border. Pima County homicide detectives Juan Caldera and Junior Collins work the case. The Border Patrol captures an illegal immigrant who saw a man dressed in army fatigues holding a rifle with a scope near the murder scene. Was he a drug or gun smuggler or a Minuteman? How could he be connected to the vics?
Was he hired by an aggrieved neighbor to avenge maltreatment in the HOA? Stymied by too many suspects and conflicting possible scenarios, the detectives catch a break when the shooter is captured in Mexico. But he escapes during the return to the U.S. and is found shot dead the next day. Then more people in the HOA die from an unusual poison apparently consumed at an HOA sponsored potluck dinner. Who was the real target? What is the motive? Who had means and opportunity?
Are the poisonings and shootings connected?