From Chopper 6 HD, the fire could be seen wreaking havoc at this 120-unit complex on Welsh Road.
Firefighters had been called out at 5:45 a.m. More than 30 units were damaged and scores of residents evacuated for a time. Flames and smoke were showing on the upper floors of the 4-story building.
"We went inside to attack this. The best way to protect the interior to evacuate people is by protecting the stairwells," said Philadelphia Fire Department Battalion Chief Anthony Hudgins
Before the blaze was put out, 80 firefighters had been summoned to the scene as the Red Cross evacuated residents to a nearby school.
"I smelled the smoke. I turned my kitchen light on, saw smoke up around there, so I knew to get out. I got my girlfriend out of bed," said fire victim Nicholas Rosmini.
"Probably 50, give or take, people coming and going throughout the course of the morning and afternoon," said the Red Cross' Dave Schrader.
But 2 hours earlier there had been an ominous warning.
"Around 3:30 in the morning, the alarm started going off for like 15 minutes," one resident told Action News.
"Around 3:30 in the morning, there was a bright flash, bright crash. The fire alarm went off in the building. I came out on my balcony. About 20 minutes later the fire truck pulled up, checked out the building, terminated the alarm," said fire victim Thomas Ohm.
The fire department responded. The building had apparently been hit by lightning, but crews found no signs of a fire brewing. The trouble surfaced later.
"The second time the alarm didn't go off. It went off after the actual smoke was starting to pour out," said resident Angel Reyes
The fire marshal has yet to make an official ruling. But a preliminary theory is it was a bolt of lightning from that powerful overnight storm that set off the chain of events here.
The fire department did not expect to announce an official ruling on the cause until Thursday.
