A 78-year-old garden lot owner installed the device at the entry to his garden shed as a protection against thieves, but decided against locking the door, police said.
The retiree's young victim was playing hide-and-seek with friends in the area when he climbed a fence to hide in the shed on Sunday. But he failed to see the warning hung in the window and was injured by a gunpowder explosion when he opened the door. The boy sustained facial burns and an eye injury which put him in the hospital for three nights.
“It's not normal to use these devices as booby traps,” a police spokesman said, “But they are freely available to those older than 18 and their misuse is difficult to regulate.”
The device, designed to kill voles and other garden pests with a charge of gunpowder, can be purchased online for €32.
The garden owner, who declined to speak to reporters, is charged with causing bodily harm and violating weapons laws.
"The allotments are not known for burglaries, it's a peaceful area where children play," the spokesman said, adding that the old man with the unique shed-security concept had apparently “just been wanting to protect his stuff.”