The five-story building at 2363 Prospect Avenue housed 26 apartments connected by a single central staircase - the only interior route between floors. The building had no Department of Buildings violations on record, though apartments on the first and fifth floors had faulty smoke detectors. When the kitchen fire reached flashover, heat erupted from the open doorway and ignited multiple layers of oil-based paint coating the stairway walls. The Daily Beast would later report that the paint burned "like gasoline." Smoke from the apartment's burning contents and the blazing stairwell walls permeated the entire building in minutes. The Fire Commissioner compared the stairway to a chimney as thick, toxic smoke rose through the building via the stack effect - the same physics that makes a fireplace draw. Smoke seeped through door frames and ventilation systems, triggering fire alarms floor by floor.

Firefighters began responding at 6:51 p.m. to what quickly escalated from a four-alarm to a five-alarm fire. One survivor on the first floor opened his apartment door and saw nothing but solid black smoke. Around 170 firefighters converged on Prospect Avenue, battling the blaze in temperatures in the teens with wind chill dropping to single digits. Some huddled together for warmth between rotations at the hose lines. Their speed was credited with saving dozens of lives, though the fire's rapid spread through the stairwell had already trapped residents on upper floors. Many on the higher floors escaped via fire escapes, but the act of opening windows to reach them gave the fire more oxygen, feeding the flames from below. It was a terrible calculation - escape required the very action that worsened the danger.

Twelve people were found dead in the aftermath. A thirteenth died at the hospital. All who perished had been on the upper floors, above the apartment where the fire started, overcome by the impenetrable wall of smoke that filled the stairwell. Mayor Bill de Blasio called it "the worst fire tragedy in at least a quarter of a century." The Bronx fire held that grim distinction for just over four years before another apartment fire in the borough, in January 2022, killed seventeen people. Among those who responded that night was Private First Class Emmanuel Mensah of the New York Army National Guard, who lived in the building. Mensah rescued four neighbors before going back inside a final time and not returning. He was posthumously awarded the Soldier's Medal.

The investigation confirmed what the Fire Department already suspected: a child playing with stove knobs had started the blaze, and an open door had turned a survivable kitchen fire into a building-wide catastrophe. The New York City Council responded with a series of fire safety ordinances. In May 2018, it passed two bills: one requiring the FDNY to develop educational programs for children and parents about fire safety, and another mandating that doors in residential buildings be self-closing by July 31, 2021. In November 2018, a third law required buildings with three or more residential units in mixed-use structures to create fire safety plans covering preventative measures and escape procedures. These laws addressed the specific mechanics of the Prospect Avenue fire - the door left ajar, the absence of fire safety awareness - but they also acknowledged a broader truth about urban fire risk: in dense, multi-story apartment buildings, the difference between a contained fire and a mass casualty event can be as small as a door that does not close behind you.