A Hawaii man was charged with four counts of assault after allegedly attacking a group of men with what is believed to be a cow’s thighbone, police on the Big Island said Wednesday.

Officers responded to a report of a brawl outside a Kailua-Kona bar on Christmas Eve and arrived to find four men with injuries from an attack. Bar patrons were holding Gregory Haas, 45, who witnesses told police attacked the men with the bone.

“He did indicate that he did actually find it in pastureland here in the Kona area,” Lt. Gerald Wike said Wednesday. The weapon was recovered at the scene and taken as evidence. Police are sure it’s a bone from a large animal and are trying to determine with certainty that it’s from a cow.

“It’s unusual someone using that as a weapon,” he said. “This is the first that I have experienced an assault taking place with what appears to be an animal bone.”

The attack in the Gold Coast Center parking lot was “unprovoked,” Wike said, adding that Haas appeared to be intoxicated.

One of the victims, 40, was hit in the head and airlifted to a Honolulu hospital in critical condition. He has since been discharged and returned to the Big Island, Wike said. Another man, 25, was treated at Kona Community Hospital for cuts to his head and released. Two others, 65 and 49, received injuries that did not require medical attention.

Haas was charged with one count of first-degree assault and three counts of second-degree assault.

A preliminary hearing has been scheduled for Thursday, according to the Hawaii County prosecuting attorney’s office. Haas could not be reached Wednesday at Hawaii Community Correctional Center, where he is being held in lieu of $55,000 bail.