A Thai para-athlete and former soldier shot his bride and three others before killing himself on his wedding day, police told the BBC.
Chaturong Suksuk, 29 and Kanchana Pachunthuek, 44, were married on Saturday in north-east Thailand.
According to reports, he left the wedding party abruptly and returned with a gun, shooting his wife, her 62-year-old mother and 38-year-old sister.
Stray bullets hit two guests, who were taken to hospital. One of them died.
Police told the BBC Chaturong "was quite intoxicated at the time", but his motive remains unclear. He had bought the gun and ammunition legally last year, they added.
Thai media, citing what guests at the party told the police, said the couple had an argument during the party. It also reported that Chaturong had felt insecure about the age gap between him and Kanchana.
But police said this was still speculation, adding that they had collected evidence and expected to close the case "soon".
Chaturong and Kanchana had lived together for three years before they married, according to Thai media.
Chaturong had clinched a silver medal in swimming at the Asean Para Games in Indonesia last year. He was also believed to be on the list of athletes competing in the World Abilitysport Games in Thailand next month.
He had lost his right leg while on duty with the paramilitary light infantry force, which patrols Thailand's borders.
While mass shootings are rare, gun ownership is common in Thailand.
Last month, three people were killed in a shooting in a luxury mall in Bangkok. And last October, a former policeman killed 37 children in a gun and knife attack at a nursery in north-east Thailand.
