Last Friday night, a group of assailants armed with guns and machetes, some in military uniforms, entered a small Burundi village near the Democratic Republic of Congo border and started attacking civilians.

According to witnesses, the assailants killed 26 people, including 11 children. At least 12 of the victims had family members in the police, and two may have been members of the ruling party’s youth league, the Imbonerakure, which may suggest they were targeted by armed opposition groups based in Congo.

“They came without warning,” one resident told me. “When I realized they were attacking homes, I ran into nearby manioc fields to hide. I returned around midnight, and I saw my nephew [2-years-old] and my niece [1-year-old], both dead. They had been shot. My grandfather was dead too; he had been stabbed. He was 87 years old.”

This is the deadliest killing of civilians in a single incident in recent years, and it comes at a tense time in Burundi. The attack occurred just days before the May 17 constitutional referendum that, if successful, will enable the president to run for two more seven-year terms beginning in 2020—potentially allowing him to remain in office until 2034. The period before the vote has been marked by widespread abuses by government forces and members of the Imbonerakure. These same forces have killed, beaten, and intimidated perceived political opponents since 2015.

In recent years Burundian security forces have carried out numerous extrajudicial executions of captured combatants and civilians. In one example, army, police and Imbonerakure members summarily executed at least 47 people between December 30, 2014 and January 3, 2015 following a clash with an armed group in Cibitoke, the same province where last Friday’s massacre took place. On December 11, 2015, security forces shot many people dead following attacks attributed to the armed opposition on four military installations.

The government should know the world is watching. The shocking killings in the village of Ruhagarika shouldn’t be used as a pretext to target former rebels who have laid down their arms, or opposition party members. In their search for the killers, the authorities should use the minimum necessary force to apprehend them and bring them to justice, not conduct extrajudicial executions.