A probe by the DOI found that human error, not the city's new 911 system, to be the culprit behind the four-minute delay in responding to a car crash that ultimately killed 4-year-old Ariel Russo in June.

The 42-page report maps the exact events that occurred between the moment that Russo and her grandmother were struck by an unlicensed driver and the time the first dispatched ambulance arrived at the Upper West Side scene.

The investigation arrived at roughly the same conclusion as a hearing held in June, in which Deputy Mayor Caswell Holloway defended the newly implemented, $2 billion system, asserting that it "sent the incident as the technology is designed to do."

According to the timeline published in the report, the delay was caused not by a technical failure, but by a dispatcher who didn't open the job because "it was not there or she did not see it." She then logged off the system and went on a break.

The crash came less than a week after the implementation of the pricey new system, which was widely criticized for crashing several times during its first days in service, forcing dispatchers to take reports by hand on slips of paper.

According to the DOI, the report is the product of hundreds of hours of interviews with employees at the city’s Emergency Medical Dispatch Center, systems and IT experts who examined the data, and information gleaned from subpoenas. It also looks at the glitches that occurred during the new system's initial roll-out in May.

“We undertook this investigation because of the public safety implications. The evidence showed no technical issues with the system on June 4th; City responses to Ariel ranged from approximately two thorough eight minutes, notwithstanding the mishandling at EMD of the calls related to Ariel," said DOI Commissioner Rose Gill Hearn in a statement. "Several outages on other dates, which played no role on June 4th, showed the need for added staffing, training and computer hardware.”

Russo's family filed a claim to sue the city for $40 million.