A 15-year-old boy was sentenced Thursday to 15 days of detention and 56 community service hours for purposely starting a March 14 fire that destroyed a vacant seed factory warehouse next door to Endeavor Elementary School in Vancouver.Clark County Superior Court Judge Robert Lewis found the boy guilty Thursday of second-degree arson following a trial prosecuted by Deputy Prosecutor Abbie Bartlett. Vancouver attorney Gayle Ihringer defended the boy against the charge.In addition to detention time and community service, the boy is required to serve 12 months of probation.He was arrested March 23 following a nine-day investigation by the Vancouver Fire Arson Team of the fire at the former Brown Seed Co. building in the Landover-Sharmel neighborhood. The fire was reported at 5:55 p.m. in the concrete-block structure at 12101 N.E. 28th St. Witnesses said they saw two teenage boys jump a fence separating the warehouse from the school campus. One was carrying what appeared to be a gasoline canister. Minutes later, witnesses heard explosions. The other boy was not prosecuted, according to court records.“He was only a witness (and) did not take any part of starting the fire,” said Vancouver Fire Marshal Heidi Scarpelli.Alan Brown, the building’s former owner, said the property was sold on March 14 after languishing on the market. The fire caused at least $200,000 in damage. The boy admitted to setting the fire but didn’t explain his motive, according to court records.The fire arson team is made up of fire marshal experts and police officers who investigate arson together. The team has a 33 percent arrest and conviction rate on arson fires, compared with about 8 percent nationwide, Scarpelli said.