Ariana Grande is inconsolable, "in hysterics" after learning at least 19 people were killed at her concert.
Sources in contact with the singer tell TMZ, Ariana is devastated that young people who came for a good time are now lying dead and injured.
We're told her next concert -- Thursday in London at the O2 Arena -- is now up in the air for 2 reasons. It may constitute a safety threat, but also, as one source put it, "She's in no condition to perform."
As we reported, Ariana had just left the stage when a nail bomb exploded in the rotunda area near the front door as people were leaving the concert. Ariana was not hurt.