"First responding units reported that when they arrived the rear of the unit was fully engulfed, and that's where investigators are concentrating their efforts," said Ogdensburg Police Chief Andy Wells.

Shannon's body was found in an upstairs bathroom. His two children were not home at the time.

Both John Shannon and his 13-year-old son testified against Wayne Oxley, the man accused of beating another man to death over drugs.

Since his testimony, Shannon received a number of death threats.

"We investigated a report from the victim as late as yesterday afternoon," said Chief Wells.

Acting District Attorney Gary Miles is looking into a possible connection between Shannon's testimony and his death. Miles says Shannon's death shouldn't be a setback in the Oxley murder case.

"We've already obtained Mr. Shannon's testimony under oath, and he was subject to cross examination. My belief under the law is that I may still be able to use that testimony since he was fully cross examined at the preliminary hearing," said Acting St. Lawrence County District Attorney Gary Miles.

The Oxley murder case is expected to go before a grand jury in the coming months. Of course the focus now remains on how the fire and just how John Shannon died.

An autopsy was performed late Thursday afternoon, but officials say it will be quite some time before those results are released.