Seven people escaped a burning apartment on Post Street in Riverside about 1:30 a.m. Monday, but a woman was injured when falling from a ladder during the rescue.
While five people got out on their own, two of the second-story residents had to pulled through windows of their apartment.
"The lady that was first coming out of the window panicked when she got on the ladder, knocked herself and the firefighter off the ladder," Jacksonville Fire-Rescue spokesman Mike Peery said. "Both of them fell out 12 feet to the ground."
The woman, Adrienne Hills, was taken to Shands-Jacksonville Medical Center, but suffered only a cut to her head and an injury to her arm.
The firefighter who also fell and a man who was also rescued from the second-floor apartment were treated at the scene for minor injuries.
Two cats, a bird and some goldfish died in the fire.
Resident Dee Thompson said her dog's barking and pulling at her wrist woke her up. She got up her husband and told arriving firefighters about the people trapped upstairs.
"I'm grateful. My husband is OK and everybody in this building is alive," Thompson said. "Everything else, it don't mean nothing. A life, you can't get it back."
Hills told Channel 4's John Dunlap that she felt bad for the firefighter, who she described as relatively small compared to her.
"I put one leg out, you know, then I started to put the other foot out. The next thing I know, my balance is gone," Hills said.
"We saw both of them hit the ground, and I'm like, 'Oh my God, please let her get up,'" Thompson said.
Firefighters said they believe a space heater in a downstairs apartment caused the fire.
The Red Cross was at the scene helping the tenants find a place to stay for the next three days.