New Delhi, Nov. 12 -- An Indonesian student suspected in last week's bomb attack on a high school mosque had assembled small-scale explosive devices at home and wanted to copy extremists he found online but had no links with any militant networks, authorities said Tuesday.

Police investigators described the 17-year-old, who was among the 96 injured in Friday's blasts in Jakarta, as a loner obsessed with violent and extreme contents. The student, who was not identified, was still recovering at a hospital after two surgeries.

"This boy had been motivated to launch such an action," Jakarta Police Director of General Criminal Investigation Iman Imanuddin told a news conference. "He felt alone and had no place to express his complaints, eith...