The ATF allowed "Nightline" unique access -- an inside look at its efforts to solve an arson case.
They used the newest and most advanced technology available to them in a manner a lot like what one might see on CBS' "CSI: Crime Scene Investigation."
The first time that lead ATF investigator Brian Grove and other agents gained access to the scene of the alleged crime wasn't until nine months after the fire, on Nov. 15, 2007.
The house on Cedar Avenue had been sitting idle. Grove and his team begin their painstaking hunt for clues, videotaping and photographing what remained of the home and taking precise measurements of the rooms.
Local authorities informed ATF that they had found evidence of gasoline throughout the home, including in the parents' bedroom.
As they worked, it was clear that ATF agents weren't simply examining the crime scene. They also collected samples from the carpet and the structure of the house. They took measurements of certain rooms, and they were also interested in the furniture.
The strategy: ATF planned to rebuild the bedroom and hallway leading to the parents' bedroom. They wanted to re-create, as best they could, what happened in New Jersey that day.
The ATF's national arson laboratory in suburban Maryland is home to one of the largest "burn rooms" in the world. The massive facility is the site of an endless number of infernos, where again and again, buildings are built up only to be burned down.
There was no evidence of another suspect in this arson, so prosecutors looked to the ATF's forensics to answer critical questions. Was it likely that the parents set the fire themselves in the hopes of getting insurance money? And if Jason Henry set the fire, had he planned to murder his parents? Or had he been so reckless that either their deaths or severe injury were likely?
Last May, ABC News cameras rolled as construction began on what would eventually be three nearly exact replicas of Stefan and Michelle Henry's bedroom.
Grove described what would happen to the newly built models in the medium burn room, which houses three structures specific to the New Jersey case.
"We will run two tests in each of the these structures, the goal being to get a better understanding of the first two to three minutes of the fire that occurred at the actual house, specifically the conditions in the bedroom where the victims were sleeping at the time the fire started," he explained.
For a time, the ATF investigators acted as contractors, locating and purchasing materials as identical as possible to those used to build the Henrys' actual home.
"What we try to do is replicate the scene as best as possible, so if we can't get the exact door frame or what you have, we try to come as close as possible," Grove said.
Sometimes, it could be challenging to find similar materials. For example, it was difficult to locate mattresses subject to older fire codes.
"We want mattresses that don't have any fire retardant on them. … Our hardest task is trying to obtain those types of mattresses, and manufactures stop making them," said one ATF investigator.
"Our next stop is hotels," he said.
Sensors, to measure everything from gas temperature to flames, were manufactured on site.