(CNN) -- Ultimate Fighting Championship star Conor McGregor has been charged with assault, police say, over allegations that he and others attacked a bus carrying UFC fighters after a media-day event Thursday in New York City.
The incident at the Barclays Center in Brooklyn left at least two athletes injured and unable to fight in Saturday night's UFC 223, set to be held at the same arena, UFC said.
McGregor, who wasn't on the UFC 223 card, was arrested and charged with three counts of assault and one count of criminal mischief, the New York Police Department said.
McGregor is accused of throwing something through the window of a bus, injuring a passenger, according to an NYPD source with knowledge of the event. Video from TMZ Sports shows someone picking up a two-wheeled dolly and throwing it into a bus window, smashing the glass.
A second mixed martial arts fighter, Cian Cowley, was also charged with one count of assault and one count of criminal mischief, police said. Cowley allegedly threw a chair at the bus.
CNN could not immediately reach representatives for McGregor or Cowley for comment.
McGregor is expected to appear in court Friday. Ahead of the court appearance, he and Cowley were seen separately Friday morning being escorted out of the NYPD's 78th precinct building and into cars, with their hands apparently restrained behind their backs.
The bus attack is just one issue clouding Saturday night's events. Fighter Max Holloway tweeted Friday that he'd been forced to withdraw from his top-billed match against Khabib Nurmagomedov for the lightweight title, which UFC is stripping from McGregor because of his long absence from UFC fights.
Holloway -- who'd only just accepted the match days ago after another fighter was injured -- was deemed unable to safely cut his weight to the required 155 pounds in time for the event, ESPN reported.
McGregor had 'beef' with fighter, UFC president says
McGregor and his entourage of about 20 people were let into the arena through a door during a media-day event by someone affiliated with a credentialed website, UFC president Dana White told the website MMAjunkie.
The group went down to the loading dock where some fighters who were to participate in Saturday's event were getting on buses.
McGregor's group attacked a bus using trash cans, metal barricades and the dolly, White said.
"This is the most disgusting thing that has ever happened in the history of the company," White told MMAjunkie, adding later, "This was a real bad career move for him."
White said McGregor had "some sort of beef" with Nurmagomedov, who was on the bus and is fighting Saturday for the lightweight title McGregor is vacating.
Two fighters injured; at least three bouts canceled
Two fighters were injured in the bus attack, UFC has said, and their UFC 223 bouts have been canceled.
Lightweight fighter Michael Chiesa and suffered head and facial cuts from broken glass, White told MMAjunkie. Chiesa later said on Twitter that the New York State Athletic Commission determined he would not be allowed to fight on Saturday.
Flyweight Ray Borg, who was scheduled to face Brandon Moreno, is also unfit to fight due to multiple corneal abrasions, according to the UFC.
"The organization deems today's disruption completely unacceptable and is currently working on the consequences that will follow," UFC said in a statement.
UFC's statement also alleges featherweight fighter Artem Lobov was in McGregor's entourage during the attack.
It said Lobov has been removed from his scheduled bout Saturday against Alex Caceres "due to Lobov's involvement in the incident." The UFC did not elaborate on what that involvement entailed.
ESPN reported that Lobov, a teammate of McGregor's, had been involved in a minor scuffle this week with Nurmagomedov at a hotel.
Despite the three bout cancellations, "UFC 223 will proceed ... with 10 bouts," the UFC said. "Moving to the Pay-Per-View main card is the featherweight bout between Zabit Magomedsharipov and Kyle Bochniak."
As of early Friday afternoon, UFC hadn't confirmed that Holloway was out of the lightweight championship match, and there was no official word on a replacement.
McGregor (21-3) last fought for UFC in November 2016, when he won the lightweight (155-pound) championship, according to Bleacher Report.
McGregor last competed eight months ago, losing to undefeated Floyd Mayweather in a boxing match that reportedly paid Mayweather more than $100 million and McGregor at least $30 million.