This March 1961 newsreel begins ‘A mammoth rally in the Workers Stadium in Peking … protesting the death of Patrice Lumumba, the slaying of the Red-inclined political leader has become the Communists’ basic reference point’.
It was widely believed at the time that Lumumba was assassinated by the Belgian government, former rulers of Congo, and the CIA. The assassination was protested against by most communist countries’ governments and by leftists in the West.
There’s a decent summary of Lumumba’s life on Wikipedia.