In just minutes, the gunman had killed three others before being shot to death by a police officer.

The rampage Wednesday night stunned the heavy metal world and left police searching for answers about what set the gunman off.

The slain guitarist, “Dimebag” Darrell Abbott, 38, was a driving force behind the rock band Pantera, and police are looking into reports from witnesses that the gunman was a fan irate that the hugely influential group broke up.

Some of the 500 people packed into the club to see Abbott’s new band initially thought that the gunman was an excited fan or that the shootings were part of the show.

“I figured it was another fan wanting to jump off the stage and crowd surf,” said Brian Kozicki, the club’s lighting designer. “I think he knew he wasn’t going to get out and he was going to take down as many people as he could.”

Police identified the gunman as Nathan Gale, 25, who listened to Pantera music to psyche himself up before football games and would often hang out at a tattoo parlor and make a pest of himself by talking to customers about music.

“We may never know a motive for this, unless he left a note,” Sgt. Brent Mull said.

Also killed were Erin Halk, 29, a club employee who loaded band equipment; fan Nathan Bray, 23; and Jeff Thompson, 40.

Two others were hospitalized after the shooting. The nature of their injuries was not disclosed.

The guitarist’s brother, Vinnie Paul Abbott, the drummer for Damageplan, was rushed to safety offstage and tearfully tried to learn his brother’s fate from officers who couldn’t even tell him which hospital he was taken to.

With his frenetic, ear-splitting guitar riffs, Dimebag Abbott created an aggressive sound for Pantera and attracted a cult following in the early 1990s. The band was nominated for Grammys in 1995 and 2001. The Abbott brothers left Pantera last year and released Damageplan’s debut album, New Found Power, in February.

“I’m absolutely beside myself with grief. I can’t for the life of me understand why someone would do this,” said heavy metal legend Ozzy Osbourne, who often toured with Pantera.

Lines were deep Wednesday night at the Al Rosa Villa club – a popular venue for heavy metal for 30 years – to buy T-shirts for Damageplan.

As the lights dimmed, club security was trying to catch up to a man in a Columbus Blue Jackets hockey jersey over his sweatshirt, who was seen jumping the 8-foot wooden fence to enter the club. The guards could not reach the tall, heavyset man in the crowd.

He climbed onstage, as many Al Rosa headbangers do.

“At first we thought it was a hoax, and then when he fired again we knew it was real,” said Jeremy Spencer, 16.

Kozicki, the lighting director, brought up the house lights and ducked under his control table, where he called 911 on his cell phone. Several calls followed, with one male caller saying: “He’s on stage right now. He’s got a gun. … He just shot again.” Fans surged toward the doors in fear.

Kozicki peeked from his table to see the gunman holding a man in a headlock. Police said the gunman appeared ready to shoot the hostage, who managed to duck just enough for Officer James D. Niggemeyer to take aim and kill Gale.

On Thursday morning, fans left flowers and a bottle of Rogue “Dead Guy Ale” outside the taped-off club parking lot.

Gale has a minor police record in Marysville, near Columbus, including driving with a suspended license last month, said Police Chief Floyd Golden. At the Bears Den Tattoo Studio in Marysville, Gale made people feel uncomfortable by staring at them and forcing them into a conversation, manager Lucas Bender said.

“He comes in here and likes to hang out when he’s not wanted,” Bender said. “The most pointless conversations.”

The shootings came on the 24th anniversary of perhaps the most well-known assassination of a rock star – that of former Beatle John Lennon outside his New York City apartment in 1980.