It was nearly 10 p.m. on New Year's Eve, 1982. Two officers on New York Police Department's elite bomb squad rushed to headquarters at One Police Plaza, where minutes earlier an explosion had destroyed the entrance to the building. Lying amid the carnage was Police Officer Rocco Pascarella, his lower leg blasted off.

"He was ripped up like someone took a box cutter and shredded his face," remembered Detective Anthony Senft, one of the bomb-squad officers who answered the call 25 years ago. "We really didn't even know that...