Human Rights Watch says that sworn testimony from six Colombian generals implicates the former head of the U.S.-backed army in the extrajudicial killings of civilians.

The Washington-based group on Tuesday revealed the testimony against retired army Gen. Mario Montoya, saying it fears that an investigation of him launched last year has stalled and crimes by the military go unpunished under the terms of a peace deal with leftist rebels intended to judge atrocities committed on all sides during the country’s half-century conflict.