[6] He became involved in several private enterprises and served in the colonial police force,[3] though he was dismissed from duty on 10 September 1952, after being repeatedly reprimanded for displaying arrogance and indiscipline.
[7] He eventually became the president of the Léopoldville chapter of the Mouvement National Congolais (MNC) and participated in the Belgo-Congolese Round Table Conference in Brussels, Belgium on the organisation's behalf.
With the independence of the Republic of the Congo in June 1960, Mpolo was elected to the Chamber of Deputies as a representative from the Lac Léopold II District.
[9] On 28 July, Mpolo was made a member of a cabinet committee established to handle Congolese relations with United Nations officials.
[9] On 23 September, Mpolo and Deputy Prime Minister Antoine Gizenga were arrested and plans were made to send them to secessionist Katanga.
Once there, they were brutally tortured at the hands of Moïse Tshombe and Godefroid Munongo, Lumumba's chief political rivals and the leaders of the secessionist state.
The following morning, on orders of Katangan Interior Minister Godefroid Munongo who wanted to make the bodies disappear and thereby prevent a burial site from being created, Belgian Gendarmerie officer Gerard Soete and his team dug up and dismembered the corpses, and dissolved them in sulfuric acid while the bones were ground and scattered.