Gunmen in eastern Congo burst into the home of a United Nations field worker, opening fire and killing him over the weekend, according to a statement published Monday on the website of the Office of the United Nations High Commissioner.

The U.N. refugee agency said that 38-year-old staff member Rocky Makabuza died on Saturday in the provincial capital of Goma after sustaining gunshot wounds to his stomach. He was shot by unidentified assailants who attacked his home last Friday night.

Makabuza was a field safety officer for UNHCR at its office in Rutshuru, north of Goma.

"Neither the identity of his assailants nor the motives for the attack have been established," the statement said.

However, his death comes on the heels of a new rebellion in Congo's volatile east, which is home to numerous militias and rebel groups. The latest violence followed a mutiny in the Congolese army after the defection of Gen. Bosco Ntaganda.

Ntaganda is wanted by the International Criminal Court for a host of crimes allegedly committed during his time as the head of a now-defunct rebel group. He and his men agreed to join the Congolese military after a 2009 peace deal. The accord led to a three-year period of relative peace, but the deal fell apart last month. Waves of defections followed, as dozens of soldiers loyal to Ntaganda followed him into the bush.

Reached by telephone, the mayor of the town of Goma told The Associated Press that an investigation had been launched.

"The police is in the field in order to try to get to the bottom of this act, and to know who is behind it," said the mayor, Jean Busanga. "It's too early to say if it was a premeditated act, or if it was a crime motivated by financial gain."

The U.N. High Commissioner for Refugees urged authorities to fully investigate the crime.

"I deplore the shooting of a colleague," said Antonio Guterres. "We do not know who is responsible for Rocky's death or why they attacked him. I hope that the authorities will do their best to investigate the incident and bring those responsible to justice," he said.