There was anger and outrage after a video of a carriage horse collapsing on a Manhattan sidewalk went viral.

“He appeared malnourished. His ribs were showing. This horse was obviously suffering,” said Caroline Smidt, who apparently saw the horse, named Ryder, in distress and having trouble walking in Central Park last Wednesday, hours before he laid down on the asphalt on 9th Avenue and 45th Street.

“This horse looked like he was about to collapse right in front of me and this man worked him for four more hours knowing he was in horrible condition,” Smidt added.

Demonstrators gathered outside the Manhattan District Attorney's Office Tuesday, calling for law enforcement to launch a criminal investigation into the carriage driver involved in the incident.

“Hours before Ryder collapsed on Aug. 10, he was struggling to walk, falling to his knees,” said Edita Birnkrant, the executive director of NYCLASS.

A bill introduced by Queens City Council Member Robert Holden would replace Central Park’s 68 remaining horse carriages with electric ones by 2024 — a goal Holden says can’t come soon enough.

“Four horses collapsed. One died in the last four months. When’s enough enough?” Holden said. “That poor horse had to go down to really change things and it was heartbreaking to see. Nobody can see that video and not feel for that horse if you have a heart.”

Many speculated that heat exhaustion caused Ryder's fall. The temperature last Wednesday was in high 80s, but it did not reach the city threshold of 90 degrees that forces hansom cab drivers to stable their horses. The hansom cab union has maintained the incident came without warning — that Ryder tripped and collapsed due to a neurological disease which can cause loss of balance.

But animal rights activists deny this assessment, claiming Ryder’s collapse stemmed from neglect.

“The fact that Ryder displayed neurological signs, muscle atrophy, poor body condition, was so underweight, these are chronic conditions, not short-term conditions,” Birnkrant said. “This is evidence of long-term neglect and criminal animal cruelty.”

Police doused the horse with water before he eventually stood back up and returned to the stable reportedly okay. Smidt says she’s spoken with an animal sanctuary in New Jersey that would be more than happy to accept Ryder into their care.

“Animals should be treated humanely and we take any incident of animal cruelty extremely seriously,” a spokesperson for the Manhattan District Attorney’s Office said in a statement. “We are reviewing the incident.”