LA HABRA When police responded to reports of a fight, they found a bloody, unconscious man outside a local bowling alley.

What they later surmised, however, was that the man had assaulted another patron at the venue, and he was arrested.

La Habra police responded around 11 p.m. Wednesday to the 13th Frame Lounge, a dive bar and music venue inside the La Habra 300 Bowl at 370 E. Whittier Blvd.

About 150 people were packed inside for a sold-out, all-ages show to see Cattle Decapitation, a “death-metal progressive grind band” from San Diego, according to the band’s Facebook page.

Several people were moshing, or slamming into one another, including a woman who was “pushed and shoved, and her boyfriend took exception to it,” police Sgt. Ron Hurst said.

“Obviously, that type of dancing lends itself to aggressive behavior,” Hurst said.

The woman’s boyfriend, identified as Adam Merrill, 30, proceeded to jump into the mosh pit and cut the right side of a 26-year-old man’s neck with a 3 1/2-inch pocket knife, police said.

Authorities said at least two men dragged Merrill outside the bowling alley and wrestled him to the ground in the parking lot.

One man was able to get the knife out of Merrill’s hand, while another hit him so hard he was knocked unconscious, Hurst said.

Police said the man with a bleeding neck was taken to UCI Medical Center in Orange and is expected to survive.

Merrill was taken to St. Jude Medical Center and was released around 3:30 a.m. Thursday. He then was arrested on suspicion of assault with a deadly weapon.

Neither of the men involved in the parking lot fight were arrested immediately, Hurst said.