Voice UK coach Jessie J was left involved in a police investigation last night after a stabbing at her BlackBerry gig.
Jessie was performing for fans, celebrities and competition winners at the Pulse underground nightclub in central London.
But what should have been a night of fun and music ended with one man fighting for his life after reportedly getting stabbed in the neck with a bottle.
Jessie tweeted this morning: "My thoughts are with the person who was seriously injured last night at the blackberry bbm party. So sad. I really hope they are ok."
All those at the gig - which included stars from The Only Way Is Essex - were kept in the club by the police until the early hours.
One onlooker told the Daily Mirror today: "People were crying and quite a lot were being sick, whether from the blood or the alcohol.
"A lot of people here were teen users of BlackBerry who don't seem to have had a free drink before."
The Met Police said in a statement today: "At around 12.07am the ambulance service called police regarding a man injured in a club off Southwark Street.
"He is thought to be in his 30s and has been taken to hospital in a serious condition.
"The victim is thought to have been injured with a bottle. One man has been arrested and is in custody."