January 25, 2004 08:17 AM EST NEW YORK - Police sent to investigate a backyard explosion that injured an artist discovered weapons and ammunition along with material related to the World Trade Center and other sensitive locations, authorities said. The discovery brought members of the Joint Terrorism Task Force to the Brooklyn home of Christopher Hackett to investigate, FBI spokesman Joe Valiquette said Saturday. Police said they weren't sure of the significance of the material, which included photos of the World Trade Center and information on the Brooklyn Bridge and a city reservoir. Hackett, 31, dialed 911 just before noon after suffering burns and head injuries while working on an art project, authorities said. He was in stable condition at Lutheran Hospital. Hackett said an explosion occurred while he was working with a propane tank and a homemade device designed to shoot confetti out of a pipe, Fire Department spokesman Sean Johnson said. Authorities found eight pounds of black powder, two high-powered rifles, a 9 mm handgun, a shotgun, a machine gun, a case of shotgun shells and 400 rounds of other ammunition, Johnson said. Richard Nelson, 15, who lives in the neighborhood, said Hackett is well-known there, and that concerns over what was found in the apartment were "out of proportion." Nelson said Hackett would take guns and turn them into something positive, like a toy for blowing bubbles. "There's not any negativity to him," Nelson said.