"The incident happened when a drunken soldier in civilian clothes fired four shots from his gun, causing panic," the mayor of Beni, Jean Edmond Nyonyi, said yesterday.
"Eight people drowned when they threw themselves in the river, four were killed in accidents and one person died of a heart attack," he said.
Fears of gun violence run deep in Beni, which lies in a strife-torn, unstable region of the DRC.
More than 700 people have died since October 2014 in massacres blamed on the Allied Democratic Forces (ADF), a partly Islamist armed group of Ugandan origin.