[1] After graduating in 1954 he worked briefly for a research institute in Leningrad before returning to Armenia to join the Yerevan Electrotechnical Factory.

[citation needed] Demirchyan was elected first secretary of the Armenian Communist Party in November 1974, effectively the leader of Soviet Armenia.

During his fourteen-year rule, Armenia was prosperous by Soviet standards, its economy helped by semi-legal and illegal businesses.

However, Demirchyan failed to quell popular demonstrations in Armenia calling for Nagorno-Karabakh to be transferred to Armenian jurisdiction, even siding with the protesters.

Four months later, on 27 October, he, along with Prime Minister Vazgen Sargsyan and 6 other senior politicians were shot and killed in the Armenian parliament shooting at Yerevan.