The fire broke out around 11 a.m. at a building along Shorepoint Court. Fire officials said the flames spread quickly from the second floor to the third floor within a matter of minutes.
Sven Rossbach said the building's fire alarm is known to go off every now and then, but he knew something was wrong when he saw smoke from as far away as the pool area of the complex.
"I saw flames shooting out of the side of the building," Rossbach said. "I couldn't believe my eyes."
Natalie Johnson, the seven-year-old daughter of the apartment manager, was given a cell phone by her mom to call emergency officials when the fire broke out.
"When I was running down into the office, I saw a lot of smoke, so I decided to call 9-1-1," Johnson said.
Outside the building, a woman consoled another resident who feared for a puppy that was left behind when the fire broke out. Some pets, including a Yorkshire Terrier puppy captured in a photograph by ABC7 viewer Chris Hirneisen, were rescued by firefighters.
Fire official Daren Olsen said the blaze began on the second floor and spread "relatively quickly" to the third floor of the building. In all, 50 to 60 firefighters were dispatched to the scene and six units were lost.
Officials told Bay City News the fire caused an estimated $1.5 million in damage.
The American Red Cross is stepping in to provide housing assistance to the families who were displaced by the fire. Electricity has been shut off throughout the building, displacing more families.
There were no reports of injuries, though two people were rescued from balconies and at least one of them was treated at the scene.
Mutual aid is being offered to help cover other parts of Alameda while firefighters continue their work at the apartment building. The cause of the fire is unknown.
Information from Bay City News contributed to this report.