Grieving relatives of 29 people murdered by a rogue soldier in Thailand held Buddhist prayer ceremonies on Monday, as questions multiply over how and why the unprecedented shooting spree happened.Holding portraits of their relatives and dabbing away tears, families of the victims arrived at a city morgue in Nakhon Ratchasima, better known as Korat, to carry home coffins bearing their dead.READ | Thai mall shooting survivors tracked killer via CCTVThe killer started his rampage on Saturday afternoon with weapons stolen from a barracks' arsenal, where he gunned down Mehta Lertsiri, 22, who was guarding the depot."I don't know what to do next," Mehta's grief-stricken grandfather, Udom Prapotsang, said outside of the morgue waiting to claim his body."His 4-year-old son keeps asking why he can't call his dad. I will remember to tell him fond stories about his dad."Bullet-riddled mallFlowers and messages of condolences mounted outside the bullet-riddled mall where a terrifying siege unfolded on Saturday night.The killer, armed with automatic weapons, held out for 17 hours as hundreds of shoppers cowered in toilets, storerooms and under tables."R.I.P. Korat, we will not forget," said one of the condolence messages left in a growing tribute outside the Terminal 21 mall in the north-eastern city.The gunman - Sergeant-Major Jakrapanth Thomma - was shot dead by a commando unit on Sunday morning, ending a rampage that left 29 dead and scores more wounded.A Buddhist monk in orange robes led a prayer ceremony on a grass verge outside the mall for Peeraphat Palasan, who was shot dead as the gunman sprayed bullets into traffic, killing the 25-year-old engineer and causing his car to crash.His father, Witoon, was among a dozen mourners crying, kneeling, hands clasped - some holding incense sticks - in prayer."My son had just finished work and came here to go shopping," Witoon said. "I never thought I would lose him so soon."Lucky survivors have recounted hiding across the mall, keeping up to speed with the gunman's movements through friends on the outside and snippets of CCTV footage shared over messaging groups.As Korat - and the country - mourned, there were growing questions about why the gunman went on a killing spree over an apparent private debt to a senior officer and how he was able to steal weapons, including an M60 machine gun, and hundreds of rounds of ammunition.Divisive Prime Minister Prayut Chan-O-Cha was hammered on social media for a tone-deaf response to the crisis during a visit to the city on Sunday where he posed for selfies, high-fived a crowd and smiled before shutting down questions from the media at a press conference."There should be no smiles, joking around and touching hands like people are your fan club," popular blogger Sorakon Adulyanon, aka Noom Muang Chan, said on Facebook.Others drew unfavourable comparisons with the dignified response of New Zealand's Prime Minister Jacinda Ardern to the Christchurch mass shooting last year.As criticism snowballed, the gruff former army chief Prayut was prodded into a rare act of contrition late on Sunday."We are all saddened by what happened," he said on his official Facebook page."I intended to offer my moral support... my expression may have been misunderstood or made many people uncomfortable."