PORT ORCHARD, Wash. -- A 17-year-old boy prosecutors said was responsible for a spectacular fire in Bremerton last summer was found guilty of first-degree arson Monday, reported KIRO 7 Eyewitness News.

The July 27, 2008, fire at Arnold's Home Furnishings quickly escalated into a spectacular five-alarm blaze that destroyed the 20,000-square-foot building and caused about $12 million in damages.

Defense attorney Tom Weaver seemed stunned by the ruling.

“The judge was apparently at a different trial than the one I was in. I don't believe that this boy did it and I believe we presented substantial evidence that he didn't do it,” Weaver said.

Police said the boy was skateboarding with two friends near the store when he broke a window and then lit a couch on fire. Weaver claimed the county’s case hinged upon the defendant’s confession to police, a confession they say was coerced.

"We never alleged they waterboarded him or anything like that. That clearly wasn't at play here, but the police repeatedly fed him information he wouldn't have had," Weaver said.

Judge Lelia Mills disagreed.

"It's important to note that the officers did not tell him what to say, the confession evolved as a give and take," Mills said.

WATCH IT: Teen Convicted Of Bremerton Arson

Sentencing is scheduled for Dec. 11. The teen, who was tried as a juvenile, could face between 25 and 32 months in juvenile detention.

Weaver said there will be an appeal.

More than 100 firefighters from Tacoma, Lakewood, University Place and Gig Harbor were called to fight the fire.

Arnold's was a landmark business in Bremerton for nearly 60 years.