for 26 years he and his wife had lived on this street in teaneck. they'd raised their two daughters here. now, investigators had to figure out who wanted him dead. >> it wasn't just a shooting, it was an execution. he shot him from behind execution style. >> diabolical? >>> yeah, despicable. >> reporter: back at the scene of the fire, investigators found a bullet casing for a .380 caliber handgun. an analysis of a comforter also found in that bedroom revealed something else. >> and the forensic scientist was able to determine that ethanol was on the comforter. >> reporter: that suggested an accelerant had been used to set rob's body on fire. for bergen county prosecutor john molinelli, that was a disturbing development. that's because this was now the arson homicide in bergen county in less than a year. >> are those other two murders the first thing that come to your mind when you see this crime scene? >> there was certainly a discussion and a deliberation on the topic, certainly within the first few weeks of the cantor murder. >> reporter: on the s

we're going door to door in teaneck, new jersey, inspecting chimneys.chimney sweep michael. inside ruben's chimney, he discovers something called creosote glaze. a tar-like byproduct from burning wood. >> the glaze is combustiblcombu. if a spark were to go up the flue, it can ignite that creosote glaze. >> reporter: removing that stuff requires more than a standard sweep. we leave the homeowner with instructions to follow up. >> yeah, of course. >> reporter: remember, if you don't have a fireplace, you might still have a chimney. chimneys in some homes connected not to fireplaces, but heating equipment like a furnace, boiler, hot water heater. one big concern here, debris falling into it and clogging the vent. pumping the deadly c.o. back into the home. we check the vent from tracy brown's furnace. >> oh, there's a bird. anybody want to look? >> is there really? >> yes. >> there sure is. we dig deeper and pull out leaves. buildup not removed. up on the roof, lead technician christopher shows us how all that debris got in. there's no chimney cap. leaving