What you are talking about happened in Berlin. A construction crew was drilling 2" dia. holes to be filled with concrete as fundations for a new building. They apparently hit the fuse of an American 1000lbs dud bomb (reconstructed from fragments, I knew the guys of the Berlin Police bomb squad back then, we often worked with them when I was still bdoing blasting work in the Civil Defense). The resulting explosion killed 3 construction workers, injuring several others. The neighbouring house (a five story brownstone) got badly damaged (foundations dislodged, roof blown off), while all window panes within 500 meters radius got shattered.
This reinforced the notion that a law in Berlin and Brandenburg requiring every building site to be searched by an unexploded ordnance team with metal detectors wasn´t that bad. (THere was another explosion back in the 70´s when a (British, if I remember correctly) long time fuse bomb decided to go of under a suburban road 50 years after it was dropped. Fortunately it happened very early on a sunday morning and nobody got seriously hurt.
Actualy, during my college days I´ve been working for a month for an ammo disposal company as a digger (Firma Halter GmbH). At this time we did a systematic search of the Tiergarten park in Berlin (a bit like Central Park in NYC) and found a lot of ammo, both dud and just dumped at the German surrender.
This bomb in CGN
now was definitely an attack, not a WW2 leftover, acc. to the latest news it was attached to a bicycle outside a shop. Police are still investigating if it was criminal or political background.