LONDON — The bells of St Clement Danes Church on The Strand chimed on the hour at 10 a.m. Gray clouds hung low over traffic-filled streets and the cold chilled to the bone.
So a pretty typical February day in central London.
It became untypical at around 11, after two young men walked out of nearby Aldwych underground, or subway, station. A few minutes later, a public announcement instructed everybody to leave the building. The trickle of commuters leaving the station became a torrent. Some of them were irate, demanding an explanation from subway workers and police. Others held their heads or limbs, seemingly wounded and in shock.
Sirens screamed and a helicopter hovered above. Police vans, ambulances, fire trucks and a large green tent for the wounded clogged the narrow lane outside the station. Dozens of first responders — fire fighters in helmets and black-and-yellow outfits, ambulance workers, police officers and delighted-looking bomb-sniffing dogs — milled around on the street.Read story on NBCNews.com >