By the time firefighters made it to the house on Post Oak Drive early Sunday morning, all inside had perished.

The Duluth inferno claimed the lives of five adults, a dog and a cat, Gwinnett County fire officials said.

Investigators say a fire pit on the back deck, which had been used the night before, may have started the fire. The identities of the deceased were not released Sunday evening.

Family members at the scene Sunday afternoon politely declined to speak with The Atlanta Journal-Constitution.

“It just happened,” a man said. He did not give his name.

The deadly blaze in this quiet community left neighbors reeling Sunday.

“They were great people,” next-door neighbor Lisa Barry said, clutching her tiny dog, Dave, to her chest. “It’s hard.”

She fought back tears recalling how the ordeal began.

Around 3:30 a.m., a woman from another nearby house, Chris Johnson, came pounding on Barry’s door. Moments earlier, Johnson had heard a loud pop and looked outside to see the crimson glow two houses down, she said.

Flames leapt from the two-story tan home located in the middle of the suburban dead end off Old Peachtree Road. Firefighters called it a “fully involved” blaze. They couldn’t get inside to look for any survivors.

Now Johnson knew Barry had to get outside before the flames spread to Barry’s house.

“The house next door is on fire!,” Johnson yelled to Barry at the door. “Get out! Get out! Get out!”

They ran to the street. Johnson was on the phone with a 911 operator, who told them to stay two houses away.

They could hear the crackling of the fire, see the flames tearing through the siding. Soon firefighters would swarm the home, but for a few moments, the neighbors were looking at the house fully engulfed in a hot-red glow.

They said they felt helpless. “We knew there was no saving them,” Johnson said. “There’s no way….”

They watched the flames and wondered who was inside, their hearts sick, they said. Ashes from the house floated in the air. It looked like it was “raining fire,” Johnson said.

Soon the fire department arrived.

“It looked like every fire truck in Gwinnett County, every EMT,” Johnson said.

Recovery efforts were hampered by a partial collapse of both the first and second floors into a basement area, Gwinnett Fire Capt. Tommy Rutledge said.

Family of the victims came and waited in front of Johnson’s house while firefighters worked. Johnson put out lawn chairs for them. She brewed a pot of coffee. She wondered what else she could do. She felt helpless again.

Barry did, too.

As she stood on her porch Sunday afternoon, she thought back to her feelings 12 hours prior. She teared up. She did again when she thought about how she feels now, knowing that five people died.

“I’m in shock and I’m just…” she said, pausing, looking away for a moment. “Sad doesn’t seem to be the right word. I just feel horrible.”

Gwinnett County Commission Chairman Charlotte Nash said Sunday afternoon that she was thinking about the fire’s victims and about the safety of other county residents.

“I am saddened by the loss of lives from this fire and will be praying for the families of the victims,” Nash said. “I also want to ask every resident of Gwinnett to check their smoke detectors and ensure every family member knows the plan for escape in case of fire.”

Staff writer David Wickert contributed to this report