A 73-year-old man and two of his grandchildren were killed in Prey Veng province’s Preah Sdech district when a decades-old explosive round that he thought had been disarmed exploded after he struck it, police said.

District police chief Chey Seng Heang said that victim Tep Phal had been in possession of a 105mm explosive shell since 1979 and, thinking it inert, was using it as a work surface in the presence of his granddaughter, 12, and grandson, 9.

“Yesterday, he was making poles for tying up cows. He was [hammering] metal pieces onto the poles and was using the bullet shell as a supporting surface. While he was doing that it exploded, killing all three,” Heang said.

The head and most of the contents of the round had been removed long ago, according to Romchek commune chief Pheung Ry, but the shell’s explosive primer was still intact.

“He put the case pointing downward into the ground, and put the pole with metal onto the trigger, and it exploded,” Ry said.

Ry said that Phal was a retired secondary teacher in the district, and noted one of his neighbours had lost a limb to unexploded ordnance in the past.

According to government figures, Prey Veng saw only one UXO casualty in 2015, and hadn’t experienced any as of February of this year, the most recent period for which figures are available.