Despite "a perfect storm of errors," though, city fire investigators never determined the fire's cause or origin, so jurors found no criminal intent, Williams said.
"This grand-jury report is really about a failure of government - the failure of Philadelphia administrative agencies to accomplish the basic functions for which they exist," the jurors wrote in the 110-page report. "There are lessons to be learned. Had city departments done their job, these deaths might never have occurred."
Neary, 60, who was set to retire from the force, and Sweeney, 25, the son of a retired fire captain, died when a wall of the burning former factory at York and Jasper streets collapsed onto them.
The jurors labeled the Lichtensteins - father-son real-estate moguls from New York - as the "most culpable people."
The pair "did not pay one dime" in real-estate taxes or water and sewer bills after buying the old factory in 2008. That added up to nearly $60,000 in delinquent taxes and $13,000 in overdue utility fees, according to the report.
Yet the city's Law and Revenue departments never collected the debts, nor seized the property. In fact, despite the fire, the Lichtensteins still own the property - and still owe the city $100,000 for demolition of the factory's gutted shell, the report said.
City L&I workers also failed massively, Williams said.
The warehouse's neighbors had long complained about squatters, copper- and wire-stripping scrappers, vandals, drug addicts and other dangers. But although four L&I inspectors visited and cited the Lichtensteins for building- and fire-code violations, "nothing ever happened," Williams said. The inspectors even testified before the grand jury that the factory was "properly secured and sealed," the report said.
"While the building owners violated virtually every regulation that got in their way, they were never held accountable for doing so," Williams added.
Jurors even faulted the Fire Department, saying officials created a "collapse zone" near the factory's exterior wall - but then didn't enforce it, placing firefighters in harm's way.
"Better training and technology might have helped prevent the tragedy," the jurors wrote.
Deputy Mayor for Public Safety Everett Gillison said in an emailed statement that the Nutter administration planned to review the grand-jury report and respond "in the days to come."
The administration has already named a special independent commission to review L&I's practices and policies, and will make recommendations in June, Gillison said.
L&I is also meeting regularly with the Fire Department to address dangerous building conditions, he said.
Union leaders from Philadelphia's International Association of Fire Fighters Local 22 plan to address the grand jury's findings in a news conference today.
"We are deeply disappointed and angry that . . . Williams has declined to pursue criminal charges against the owner of the derelict Kensington warehouse that claimed the lives of Bob Neary and Dan Sweeney," said Joe Schulle, the union's president. "We are withholding our more detailed response until . . . we've had the chance to review the D.A.'s decision and consult with the Neary and Sweeney families."
On Twitter: @DanaDiFilippo