A 79-year-old man caught three youngsters red-handed as they stole plums from a tree in his garden in Bielefeld, North Rhine-Westphalia.
He saw the pilfering trio taking fruit from overhanging branches of a tree growing in his garden, but from the other side of the fence.
When the kids ignored his warnings, the man chucked a bucket of water at them and pelted them with shards of glass.
When they still showed no signs of leaving, the furious pensioner reached for his air rifle and fired several shots.
Although the man denied having aimed directly at the youngsters, one eleven-year-old boy was taken to hospital after having been hit on the wrist by one of the man's bullets, police said on Thursday.
Police said they are now investigating the man on a charge of grievous bodily harm.