For almost five years, Brandon Bryant worked in America's secret drone programme bombing targets in Afghanistan and elsewhere.
He was told that he helped to kill more than 1,600 people, but as time went by he felt uneasy with what he was doing. He found it hard to sleep and started dreaming in infra-red.
Brandon Bryant told Witness about his doubts and the mission that convinced him it was time to stop.
Witness is a World Service programme of the stories of our times told by the people who were there.