An active communist in Kosovo, he was arrested on 18 July 1941 near Rožaje, and sent to a concentration camp near Peqin in Albania. He managed to escape with the support of the Albanian communists a few months later. He and Dušan Mugoša were the Yugoslav delegates that in 1941 helped the Albanian communist groups unite and create the Communist Party of Albania. The two had been sent to Albania on the directive of the Central Committee of the Communist Party of Yugoslavia, chosen for their revolutionary experience and political knowledge, to be available to the Albanian communists; they were the most active regarding Yugoslav–Albanian alliance. Mugoša and Popović were members of the Regional Committee KPJ of Kosmet. Popović left Albania in September 1944. He was killed on 13 March 1945 in Pristina by two Kosovar Albanians, Haki Taha and Qazim Vula, both members of the anticommunist Albanian National Democratic Movement. Taha killed himself right after murdering Popović, whereas Vula was arrested and given a life sentence, but managed to escape from the prison of Niš, and fled to Albania, where he was again arrested. Vula died in 1987. Sources disagree about the motives of Taha and Vula: while the Yugoslavian regime said that the two killers were motivated by anti-Serbian sentiments, communist Albania's version was that they were used as kamikaze by the Yugoslav secret police, who wanted to eliminate Popović for his pro-Albanian sentiments. Inside the CPA and the CPY relationship, Popović always took a pro-Internationalism and pro-Albanian stance. In a party meeting of 1946 in Mitrovica, Kosovo, as a delegate of the Central Committee, he stated: "Albanians during the old Yugoslavia were oppressed, robbed economically, spiritually negated or even physically exterminated, and don't need to wonder why they had eagerly welcomed the Germans, as they were for them the liberators from the former government". The Albanian side vaguely supported the Yugoslav version at the time regarding his assassination, but after the Yugoslav-Albanian split in 1948 they accused the OZNA of having set it all up.
