He took the war relic home with him, and his son immediately alerted the police.
The grenade was damaged and in danger of exploding, so a bomb squad carried out a controlled explosion on the spot.
Houses in the vicinity of 500 metres were evacuated and the nearby Steyrtal road was closed. Luckily there were no casualties and no damage to any nearby property.
It’s not clear if the grenade dated from WWI or WWII.