It was still busy inside Bottoms Up Tavern when the gunfire started.

The Lakers game had been on TV Tuesday night. That and a birthday party meant 25 to 30 people were still at the North Long Beach sports bar just after midnight.

Alfred Zambrano was in a booth with some friends when they heard a popping sound. It took a moment before he recognized it as gunshots.

Zambrano realized a man he’d calmly smoked a cigarette with earlier in the night was now shooting.

As dozens of people fled, the gunman shot two employees, killing a bar-back and wounding a cook, according to police and witnesses.

But the gunfire ended quickly. A Long Beach police officer who happened to be nearby rushed to the bar’s door and shot into the building, according to authorities. It appears a customer may have also tried to intervene, shooting his or her own weapon, police said.

Later, when officers searched the building, they found the gunman dead, still with his weapon in hand, authorities said.

Police said they don’t know yet whose bullet killed the gunman, but they’re convinced the quick response helped prevent more violence.

“It’s really the department’s belief that those who reported the incident to our officer who happened to be in the area and the quick actions of all of the officers involved prevented potentially additional casualties from occurring,” LBPD spokeswoman Shaunna Dandoy said.

Councilman Rex Richardson, who represents the area, put it more directly in a statement: “Quick and decisive actions saved lives.”

It’s not yet clear why the suspected gunman opened fire.

Witnesses said he wasn’t a regular at Bottoms Up but he had been hanging out there in the hours before the shooting. Authorities haven’t identified him publicly.

Police said he confronted a bar employee, whom witnesses identified as a cook, before shooting him.

Zambrano said he came across the cook as he ran out of Bottoms Up. He, too, was trying to flee after being shot in the shoulder.

“He’s like, I’m hit. I’m hit,” Zambrano said.

The two men piled into Zambrano’s car and headed toward the hospital.

Inside Bottoms Up, there was more chaos. As most people ran out, a handful tried to hide.

One woman, who asked not to be identified, said she ducked into the bathroom because it was the closest door. There, she and a few others huddled in the dark, listening to the gunfire and wondering “when was it going to stop?”

As most customers ducked for cover, it appears someone at the bar tried to defend against the gunman. Investigators said they found a bullet casing that didn’t match the shooter’s or the officer’s gun.

Police suspect this came from a patron who exchanged gunfire with the attacker, but it’s not clear who that person is.

Even after the shootout, the gunman kept firing, according to police.

They say he moved through the business and shot another employee. This time, the wound was fatal, according to police.

As the gunfire continued, someone fleeing the bar flagged down a nearby Long Beach police officer and told him what was happening, authorities said.

The officer could hear the gunfire as he approached Bottoms Up, police said. Once he was close enough, the officer saw the gunman inside and shot at him through one of the bar’s doors, according to the LBPD.

But he then lost sight of the gunman, and police quickly called in any SWAT-trained officers who were on duty, police said. A neighbor said he watched them take cover outside as they appeared to be trying to communicate with the suspect.

Eventually, officers moved in and found the suspected gunman wounded and unresponsive, police said. He died at the scene, according to authorities.

As the chaos was unfolding, staff and bar regulars tried to wrap their heads around what was going on.

Longtime customers started calling the bar’s owner, Suzanne Blevins.

“They just said an active shooter was inside the bar,” she said.

Blevins headed to the scene where a handful of regulars and staffers gathered, waiting for news.

Even Zambrano came back. He said the cook ended up asking him to turn the car around and head to the bar where an ambulance took him to the hospital.

Video from the scene shows Zambrano holding the cook’s wound as he walks down Artesia Boulevard through a mass of police cars parked near the bar at Rose Avenue.

Wednesday morning, a group was still gathered by the police tape.

The bar has a rough reputation, according to a neighbor, who said there’s been frequent fights and arguments. In the wake of the shooting, Councilman Richardson said he plans on looking for new ways to address “nuisance activities and establishments” associated with crime, violence and blight.

But Cindy Marquez, who has bartended at Bottoms Up for 12 years, said the place is like family.

“We all know each other; we all drink,” she said. She’s even the godmother of Blevins’ son, she said.

Marquez wasn’t on duty Tuesday night, but her 44-year-old brother, Manny, was working a bar-back shift.

Around 9 a.m., a police detective came up to the crime tape and told Marquez they believed her brother was the one killed by the gunman. The coroner hadn’t given official word yet, but his clothing and tattoos matched his description, Marquez said.

“I don’t even understand what’s going on,” she said, wiping away tears with the front of her sweatshirt as a member of the group hugged her.

Manny had worked at the bar only a few months but endeared himself to the staff there, according to his sister.

“Everybody liked him because he would help anyone with anything whether it was helping out behind the bar or changing a tire,” she said.

Nearby, Manny’s longtime girlfriend and his mother covered their faces and cried.