It's bad.
"There was blood everywhere, there were bodies everywhere," said one who was inside the hall. Armed gunmen took hostages and began shooting them during the concert, in what looked like a series of coordinated terror attacks across Paris at seven different locations.
France 24 reports that police stormed the building at about 11.30 London time/12.30 Paris time, and two gunmen were killed. Hostages left the building, some running, some with hands on their heads. Some were shot from a balcony as they left, a witness told the France 24 TV channel. The attackers threw explosives at their victims inside the concert hall, France 24 reported.
Angelique Chrisafis, a Guardian reporter in Paris, talked to witnesses including Marc Coupris, who went to the concert with a large group of friends:
"It was carnage," said Marc Coupris, 57, still shaking after being freed from the hostage-taking at the Bataclan concert venue. "It looked like a battlefield, there was blood everywhere, there were bodies everywhere. I was at the far side of the hall when shooting began. There seemed to be at least two gunmen. They shot from the balcony. Everyone scrabbled to the ground. I was on the ground with a man on top of me and another one beside me up against a wall. We just stayed still like that. At first we kept quiet. I don't know how long we stayed like that, it seemed like an eternity. I saw my last final unfurl before me, I thought this was the end. I thought I'm finished, I'm finished. I was terrified. We must all have thought the same. Eventually, when a few gendarmes came in slowly we began to look up and there was blood absolutely everywhere. The police told us to run."
Another attendee said:
Jérome Boucer, shivering in the cold night wearing a white shirt splattered with the blood of the victims and wounded said: "The concert had started. I was in the audience and I heard what sounded like a fire-cracker. It was loud but the gig was very loud and I thought it was something that was part of the show. I think lots of people did too. Then they started firing. I saw what I thought was at least two people, then I fled. The exits were clearly marked and I just ran. There were wounded, there was a lot of blood. Blood everywhere."
A third:
"It was horrible, there were so many corpses, I just can't talk about it," said a bearded man in a death metal t-shirt as he ran down the street from the Bataclan in shock.
The Guardian has an excellent live blog with updates.
The police operation secured the building shortly before 1 am Paris time / 12 midnight London time.