A driver hit at least four Denver police officers during a Ferguson protest at a local high school Wednesday, Denver CBS reported. Authorities were assisting with the student strike at East High School when the officers were struck.

One of them is said to be in critical condition, according to a tweet from the Denver Police Department. Another was listed in stable condition and two have been released from the hospital. Three of them served in the police department for nine years and one had 17 years of service.

A police officer might have been dragged by the car for a block, a source told Denver CBS, but it’s not clear if it’s the same officer who was listed as critical.

Denver Police Department Chief Robert C. White said Wednesday was “not our best day,” in regard to officers being seriously hurt.

One of the nurses at the scene was reportedly covered in blood, the Denver Post wrote.

The driver, who has not yet been identified, was taken to the hospital with a “medical issue.” He is reportedly in stable condition. Photos of his black Mercedes from CBS Denver and the Denver Post show significant damage to the front driver’s side of the vehicle.

Pictures of the protest posted by CBS show hundreds of students blocking an intersection. The students were apparently walking from their high school to the state Capitol, signs in hand.

Wednesday’s protest comes nine days after a grand jury chose not to indict officer Darren Wilson for the fatal shooting of Michael Brown. On the same day, people in New York began to rally after a grand jury decided not to indict New York Police Department officer Daniel Pantaleo for the death of Eric Garner, who was put in a chokehold after he allegedly tried to sell cigarettes illegally.

Follow me on Twitter @mariamzzarella