Seungri got a little too close to the firework canon
And in addition to getting hurt by the firework, he sprained his already injured ankle. He was carried off by the crew and taken to the hospital.
The pain was too much for him that he actually passed out.
Afterwards, Seungri wrote an apology letter to the fans for leaving the concert early and was even performing the next evening out of stubborness.
remember this when anybody says anything hateful towards Seungri