A military court sentenced a Congolese military colonel to death and convicted three soldiers following the deaths of more than 50 people who were protesting the U.N. peacekeeping mission earlier this year.

Col. Mike Mikombe, former commander of the Republican Guard in the eastern city of Goma, was sentenced Monday. Congo has not enforced the death penalty in more than 20 years, effectively making it a life sentence.

Three other second-class soldiers from the same unit were sentenced to 10 years in prison. Two other officers were acquitted, including Col. Donat Bawili, who headed the Congolese armed forces regiment in Goma at the time.

In August, Goma’s mayor had banned a protest organized by a sect known as Wazalendo. Its supporters planned to demonstrate against the regional East African Community organization and the United Nations peacekeeping mission in Congo.

The U.N. mission has faced increased pressure to withdraw from Congo after more than two decades in the conflict-burdened country.

Advocacy group Human Rights Watch said that before the protests could take place, armed forces fired on Wazalendo demonstrators in the streets.