A New Haven Police Department cruiser collided with a CT Transit bus on the corner of Elm and Temple Streets on Monday morning, knocking officer Victor Herrera unconscious as his vehicle slammed into a concrete block on the curb of the New Haven Green.

The incident sent Herrera to the emergency room at Yale-New Haven Hospital and the woman operating the bus, as well as 23 of her passengers, to area hospitals. No fatalities were reported. A number of children on the bus appeared visibly shaken as they awaited the arrival of emergency medical technicians.

Two squad cars were responding to a call for service at Union Station, where a fight had broken out involving a “deranged person,” when one of them barreled into the bus, according to NHPD Chief Dean Esserman. Eyewitnesses on the scene said they saw two cruisers zipping down Elm Street with their sirens on as the bus moved southwest on Temple Street.

Megan Kairiss, a high school student at Haddam-Killingworth High School, said the first cruiser passed the intersection safely before the second car collided with the bus. The cruiser ricocheted into a cement block on the western corner of the intersection as the bus swerved onto the Green across Temple Street, colliding with two lampposts. One pole went through the bus’s front windshield, the other came to rest on top of the bus.

“It sounded like a dump truck hitting the ground after falling from two stories up,” said Kevin Swingle, who was standing at the curb at the time of collision, which police marked as occurring at 11:05 a.m.

New Haven Mayor John DeStefano Jr., who was on the scene to attend a Veterans Day ceremony at Center Church on the Green, said Herrera sustained serious injuries but was taken to the emergency room in a stable condition. New Haven Fire Department Chief Michael Grant said firefighters were called to the scene and had to use hydraulic tools to force the driver’s side door open to free Herrera.

Officer Mark Foster and NHPD Spokesman David Hartman confirmed that Herrera was knocked temporarily unconscious by the air bag in his vehicle.

“Thank God the airbag deployed,” Esserman said, adding that it was emotionally difficult to watch firefighters pulling Herrera, who has been with the force for nearly 19 years, from the cruiser. In a subsequent press statement, Hartman said the officer is being treated for injuries that are serious but “not life threatening.”

The woman operating the bus sustained less serious injuries, Hartman said, as she was able to walk with family members to the ambulance. He said eyewitnesses alleging that the bus driver was speeding ignored the difficulty of suddenly stopping a vehicle of that size. Kelly Bowe, who was on the scene when the crash occurred, said it seemed as if the bus driver tried to slow down but that the vehicle was already in the intersection before the driver could avoid the cruiser.

Esserman said the investigation into the crash is still ongoing and that all eyewitnesses seem to be cooperating with detectives. Hartman added that it is unlikely there will be a finding of fault or a discovery of contributing factors for weeks.

The entire intersection was closed off following the crash, with squad cars stationed on the corner of College and Elm Streets to redirect traffic. By around 3 p.m., traffic had returned to normal.

Monday’s incident marked the second time in just over three months that a collision at the Elm-Temple intersection has forced a police car into a stone post by the Green. In early August, a Cheshire teen ran a red light and crashed into a cruiser, which then hopped the curb and collided with a cement block.