Looking remarkably composed in a room packed with the families of his victims, Carl Cooper pleaded guilty Tuesday to a series of gruesome murders and armed robberies — including the 1997 shooting deaths of three young workers at a Starbucks coffee shop.

By accepting the plea, Cooper avoids a trial — and a conviction that could have brought the death penalty. As part of a deal with prosecutors, Cooper, 30, agreed to spend the rest of his life in a federal prison without the chance of release.