Flames were shooting through the roof of the The Preserve at Cedar River apartments when firefighters arrived about 1:30 p.m. Monday.
Jacksonville Fire-Rescue said the fire started on a ground-floor unit and spread to the apartment above it.
Resident Christian Purser had already tried to make sure everybody was out.
"I wanted to make sure that, since kids are off school today, that nobody was home," Purser said. "Him and I went and banged on all the doors and we went around the back and there was just a huge flame, so we said, 'We got to find something to put it out,' so we grabbed the fire extinguisher from the back, but the flame, it was way to powerful."
There were no injuries to residents or firefighters in the fire.
At least two unit was destroyed and others were damaged.
Red Cross volunteers responded and assisted residents from three affected units. The Red Cross helped four adults and two children with financial assistance for temporary lodging and replacement of necessities like food and clothing, a Red Cross spokeswoman said.