Police and crime lab technicians began investigating Thursday the deaths of a couple inside their east Kennewick home. They are believed to be the parents of a 43-year-old suspected gunman who went on a deadly rampage Wednesday, killing his neighbor and wounding another man before igniting a series of fires. He died inside a burning pickup in West Richland when the truck caught fire during a police chase that ended in an exchange of gunfire with officers. Nearly six hours later, the Kennewick couple were discovered dead in their home by a family member who had gone to check on them after he had not heard from them for a day. He told emergency dispatchers that they had been “murdered.” Investigators from various police agencies throughout the Tri-Cities spent Wednesday and Thursday methodically processing the series of crime scenes that stretched some 20 miles, from east of Kennewick to Van Giesen Street in West Richland.