In July 1992, General Kobbekaduwa was preparing for a new offensive to recapture the Jaffna peninsula which was under LTTE control, it was code named "Operation Final Count Down". Since the launching pad for the offensive was the island of Kayts on 7 August, General Kobbekaduwa moved to Karainagar naval base by helicopter with his staff. He spent much of the night planning the upcoming offensive with Brigadier Vijaya Wimalaratne, Jaffna Brigade Commander and Commodore Mohan Jayamaha. Due to concerns of the navy about the staging area it was decided to visit the Araly point the next day. At 8:00 am the group made up of Maj. General Kobbekaduwa, Brigadier Wimalaratne and Commodore Jayamaha along with several other officers headed out on a naval patrol boat towards Jaffna and returned to Kayts pier. On returning the party was met by three Land Rovers, the General, the Brigadier and the Commodore got into the Land Rover UHA 8752 with the rest of the army personal taking vehicle no UHA 8785 and the naval personal taking 5959. From there they set out to Araly Point. Half way the General order that they all use one vehicle as to not to attract fire form LTTE units in the Jaffna peninsula which was only half a kilometer away. They reached Araly Point and had a discussion and headed back when the Land Rover was consumed by an explosion. Major Rupasinghe and Major Induruwa who were 400 yards away from the incident ran to the location to find all but General Kobbekaduwa and Commodore Jayamaha alive. Killed in the explosion was Brigadier Wimalaratne, Lt. Colonels G.H. Ariyaratne, A. Palipahana, H.R. Stephen, all three battalion commanders, Lieutenant Commander Asanga Lankathilaka, Lieutenant Commander C.B Wijepura, Major Nalin S. De Alwis; the General's Aide-de-camp and Corporal Jagath Wickramaratna. The two wounded officers were rushed to the helicopter waiting to transport the group to base, which took them to the military hospital in Plalay where it Commodore Jayamaha was found dead on arrival. General Kobbekaduwa who was conscious was then transferred to the Colombo General Hospital for surgery via helicopter. Where a specialist team of surgeons were unable to save his life. He was posthumously promoted to Rear Admiral. At the time of his death he was the third most senior officerin the navy. A memorial service was held for the Admiral at All Saint's Church, Borella presided by the Cardinal Malcolm Ranjith, then Auxiliary Bishop of the Archdiocese of Colombo. Weera Mohan Jayamaha MMV in Dambulla was named after him and a statue of Admiral Jayamaha was erected in Ratmalana.
Family
Admiral Jayamaha was married to Vinodhra, they had a son and a daughter.