In case anyone asked later, he wanted documentation of some of the obstacles - in addition to temperatures near 100 degrees - that hampered his depleted department's ability to battle the fire that left at least 16 families, including 30 adults and 35 children, without homes.
He photographed a fire hydrant a block away from the hottest part of the fire. Like two others nearby, the brass threadings used to connect hoses had been stolen, leaving the hydrants unusable and delaying firefighters' ability to begin the firefight in the crucial early moments after they arrived Thursday afternoon.
Unable to take water from a nearby hydrant, he said, six engine companies had to pump water several blocks from the Cooper River.
As they got water, the chief said, crews watched buildings catch fire that looked like they could have been saved.
Harper said the department is working with the water companies that serve the city to try to get an accurate weekly list of which hydrants don't work.
"When you don't get no water, you can't do anything," said Harper, a longtime firefighter who became chief in January.
The fire was devastating, burning at least parts of about 23 buildings. City officials, the American Red Cross and social service agencies were working to find new housing for the families whose homes were burned.
Dozens more were at least temporarily without electricity and contending with smoke damage.
Harper said three firefighters and one civilian were hospitalized, all for smoke inhalation. None had life-threatening injuries.
Harper said it might take weeks to determine what sparked the fire, which is believed to have started in the building that was rented by the tire distributor Reliable Tire Co. from 1964 until 1999. It appears to have been vacant for much of the time since the company moved out and no tires were left behind.
Some reports Thursday, including one from The Associated Press, described the building as a former tire factory. But a representative from the company says tires were not made there.
Like much of Camden, a city that consistently ranks as one of the nation's most impoverished, the area near the Parkside neighborhood where the fire broke out is a hodge-podge of businesses and homes, some vacant and some occupied.
The water wasn't the only challenge.
In January, the city, facing a deep fiscal crisis, laid off about one-third of its firefighters. Several have been hired back. But Harper said the smaller force means that reinforcements from elsewhere have to be brought in sooner.
And that's difficult, he said, because they don't know the lay of the land in a city that's so different from its suburbs.
Crews had to rest frequently because of the heat of the day, the hottest since July.
The thick plume of smoke meant the PATCO trains that take commuters from southern New Jersey to jobs in Philadelphia had to be shut down during the evening rush hour. Trains resumed by 7 p.m.
Around 8 p.m., there was a new environmental problem: a thunderstorm.
While the rain was welcomed as an aid, the lightning wasn't. Ladders positioned to fight the fire from above had to be lowered for fear they'd be struck.
By the time the fire was under control later Thursday night, power transformers had melted, some propane tanks burst, several homes were reduced to rubble and a van was left charred almost beyond recognition.
Harper said embers fell throughout the neighborhood, igniting a fire on a porch more than a block from the blaze.
A building across the street full of wood pallets and sawdust was kept from burning.
On Friday, demolition crews were knocking down the remaining unstable walls of the tire building, in the hopes that investigators could soon get to the area where the fire is thought to have started. Crews from the electric company PSEG were assessing how they might be able to restore power.
And Walter Nokes, who lives a block from the fire, said he had to keep his daughter home from school. All her clothes smelled of smoke, he said.
One tidy house on one of the devastated blocks appeared untouched by the fire.
"That house," Chief Harper said as he looked at it, "is blessed."