On completing his training he was commissioned as a Second Lieutenant in the Sri Lanka Armoured Corps (SLAC).

In 1985, the army formed a Combat Tracker Team under the command of Major Hettiarachchi consisting of two officers and 38 men to conduct direct action and covert reconnaissance against LTTE units operating in the thick jungles in the northern part of the island in small groups.

This was the inception of the Special Forces Regiment which was officially formed on 10 December 1988 with Major Hettiarachchi as its commanding officer.

[1][2][3] In July 2005, the President of Sri Lanka appointed Major General Hettiarachchi as the Director General of the Disaster Management Centre (DMC) tasked with establishing the Disaster Management Centre following the 2004 Indian Ocean earthquake and tsunami, in which capacity he served till May 2014.

He is also a Fellow of the Academic Commons of the Disaster Resilience leadership Academy of the Tulane University.