The arson investigators who worked to determine the cause of the deadly fire would become critical to Willingham'sultimate conviction for triple homicide. One, Douglas Fogg, was a high-school graduate and recipient of a Purple Heart for his service in Vietnam and had been fighting fires for more than 20 years by the time he worked on the Willinghamcase. By then, he was a certified arson investigator. Fogg investigated the Willinghamfire with Manuel Vasquez, a deputy fire marshal and arson investigator who had investigated more than a thousand fires in hiscareer. Soon after their initial examination of the home, the men concluded that somebody had poured liquid accelerant throughout the twins' room and had then poured additional accelerant along the adjoining hallway and out the front door, in effect creating a wall of fire that would have prevented anybody still in the house from escaping. They based their conclusion on the following findings:• There was deep charring along the base of the walls, which the investigators felt indicated that the fire had burned extremely low down, making it unusual.• There were unusual char patterns shaped like puddles on the floor in the hall.• There were similarly unusual char patterns in the twins' bedroom. Investigators traditionally call such puddle shaped patterns "pour patterns" or "puddle configurations" because they suggestthat a combustible liquid was poured on the floor, causing fire to concentrate in the pockets of liquid.• The fire had burned through layers of carpeting, tile, and plywood flooring, and the metal springs under the twins' beds had turned white. The investigators concluded that intense heat had radiated beneath the beds and that the floor was more severely burned than was the ceiling, something Vasquez described as "not normal."• Glass from the broken windows contained a pattern consistent with what arson investigators call "crazed glass." The patterns suggested to the investigators that the fire had burned "fast and hot," suggesting that it had been fueled by an accelerant.• The fire appeared to have traveled from the twins' bedroom and into the corridor, where it then turned sharply to the right and proceeded out the front door. Fogg and Vasquez were surprised to see that even the wood under the door's aluminum threshold was charred, and, outside the front door, they noticed brown stains on the concrete floor of Willingham'sporch, which they again concluded supported the idea that accelerant was used.• Three V-shaped soot marks were on the walls, which patterns, the investigators concluded, indicated places where fire had originated. The patterns were in the hallway, in the children's bedroom, and at the front door.On the basis of these and other factors, the men quickly concluded that the fire had been intentionally set.