Thirty seconds.

In less time than it takes most people to listen to a weather report, Officer James Niggemeyer had to make a life-changing decision. He had to instantly familiarize himself with a chaotic murder scene inside a dimly lit rock club, crawl across a stage full of equipment, take aim and fire his shotgun at close range, preventing Nathan Gale -- who was holding a gun to a hostage's head -- from killing any more innocent people ...

In 30 seconds.

That's how long it took the Columbus, Ohio, police officer to assess the situation inside the Alrosa Villa on the night of December 8, when he fired the shot that stopped Gale's rampage, which left five people, including Gale and Damageplan guitarist "Dimebag" Darrell Abbott, dead (see [article id="1494653"]"Dimebag Darrell, Four Others Killed In Ohio Concert Shooting"[/article]).

Six months after that unforgettable night -- the first time Niggemeyer, 31, had fired his gun in five and a half years on the job -- and just a few days after telling his story for the first time to a local TV station, Niggemeyer spoke to MTV News about the split-second confrontation with Gale that still plays in his mind.

"I remember I was leaving my substation, which is about two miles from the club, when a call came in as a '43 at the Alrosa' -- which is police code for a shooting," said Niggemeyer, who was not allowed to speak until this week due to a grand-jury investigation into the shooting, in which he was cleared of any wrongdoing (see [article id="1502740"]"Officer Cleared In Shooting Of 'Dimebag' Darrell Abbott's Killer"[/article] and [article id="1503615"]"Officer Who Felled Dimebag's Killer Breaks Silence"[/article]). "Then, additional calls were coming in about what the suspect was wearing and more shots fired. I was on my way there, so I was the first to arrive on the scene."

Niggemeyer said he was in front of the club less than two minutes after the first call came in, and had to fight his way through a crowd of panicked fans fleeing across the street to their cars in order to get into the club's parking lot. The situation was so chaotic that Niggemeyer said he doesn't recall hearing any shots from inside the club once he was on the scene.

He had been assigned to carry a shotgun that night, which was coincidentally the same model he had at home and used for hunting on weekends.

"There was a group of people standing by the back door and they called me over to come that way as other officers were arriving on the scene," recalled Niggemeyer, who said he had driven past the club numerous times over the years, but had never been inside.

As at least five officers entered the front of the venue, Niggemeyer focused on the imposing figure of Gale, a 25-year-old ex-Marine. He saw the body of one of the group's security staff members sprawled out on the front of the stage and Gale mid-stage, holding an unidentified hostage in a headlock.

"There's no doubt in my mind that [Gale] didn't know I was there," Niggemeyer said. "From where I was, I could see he was focused on the other officers coming in the front." As Gale, who had already shot and killed Abbott and three others, was looking toward the other officers, Niggemeyer crawled through the piles of equipment on the small stage.

Though Gale did not fire any shots while Niggemeyer was inside the club, he was silently waving his 9-mm handgun at the crowd. "I was still hoping maybe he'd let the hostage go and retreat," Niggemeyer said. "I was just trying to get as close as I could to assess the situation and hoping he'd [release] the hostage so I wouldn't have to shoot. But then, while he was waving the gun around, he took it and stuck it to the hostage's head ... which changed the whole situation, if he was going to possibly execute the hostage. They never mentioned a hostage on the radio calls. I knew at that point he wasn't going to let this guy go, and [might] do something to him."

With the hostage's head positioned just under Gale's chin, Niggemeyer -- who said he had only shot deer before -- leveled his department-issued shotgun and aimed for Gale's head.

"I knew from that distance I could shoot the suspect, as long as I aimed high enough and wouldn't hurt the hostage," he said. "At that point, almost immediately, I fired." Gale, felled with a single shot, slumped to the ground. By the time Niggemeyer walked to the front of the stage, two other officers had approached Gale's body. In a video released on June 3, a club security guard can be heard telling Niggemeyer he did what he had to do, but the officer said he was so numb at that point he doesn't recall anyone speaking to him. "I was pretty shook up from having to shoot somebody," he said.

After the incident, Niggemeyer took the department's regulation three days off and saw a psychologist. "It seemed like all I did for those three days was run and rerun it through my mind," he said. "You keep seeing the people who got shot, the ones who were laying there, just on continuous replay." Now, every time he drives by the club, hears the name of the street it's on, or even hears the phrase "heavy metal," he thinks of that night.

Niggemeyer, who hasn't fired his weapon on the job since, said he recently went to the club to film an interview and owner Rick Cautela thanked him again for his heroism. "He wanted to remind me of how many lives I saved in his club," Niggemeyer said. The officer, who said he had only heard of Dimebag's previous band Pantera before the incident and had never heard their music, said he's gotten a lot of supportive e-mails in the months since from the group's fans, as well as a letter from Gale's mother.

"She wrote me a few weeks after and told me she understood that I was just doing my job," he said. "And she didn't have any ill will toward me."

Click here for more on the tragic death of Dimebag Darrell and the Ohio club shooting.