Google might not be your friend, in this case.
Everybody and their dog has video phones, now.
You were warned.
The other horse in that article got "his hind leg got caught in the carriage shaft, causing him to hit the ground". He tripped, he didn't collapse.
Pumpkin's bridle broke and horse followed his usual route within Central Park and exited the park at where a group of horse carriage drivers were waiting to corral him. No one was hurt.
This is the abuse the horses, the drivers, and their passengers face constantly.
What they don't tell ya is Oreo was working his regular shift when a bundle of scaffolding at a nearby construction site crashed to the pavement. Startled by the unusual loud noise, Oreo bolted and headed west in the direction of his stable. He was calmly waiting at a red light on 9th Avenue, when he was approached by pedestrians and police officers. The cops shot him with tranquilizers which caused him to collapse ... giving the RARAa a wonderful photo opportunity. Here's a video a passerby took of the horse before the police arrived.