The building was doomed from its blueprints. Originally designed as a four-story residential apartment building, the plans were altered by Lee Joon to create a department store. When the original contractor, Woosung Construction, refused to carry out the changes due to structural concerns, Lee fired them and used his own company to finish the job. The store opened on July 7, 1990, attracting an estimated 40,000 shoppers daily. What those shoppers could not see was that the concrete columns were only 60 centimeters in diameter instead of the required 80, and contained just eight steel reinforcement bars instead of sixteen. The building had roughly half its designed strength. A fifth floor with heavy restaurant equipment was added after initial construction, further straining columns that were already inadequate. Fire shields installed around the escalators required cutting into the support columns, reducing their diameter even more.

Investigators eventually pinpointed the final straw. Two years before the collapse, three massive rooftop air-conditioning units were moved to the opposite side of the building after neighbors complained about noise. Rather than lifting them with cranes, workers placed the units on rollers and dragged them across the roof, cracking the slab beneath their weight. Column 5E took a direct hit. Over the next two years, every time the air conditioners switched on, their vibrations radiated through the widening cracks into the support columns. On the morning of June 29, the fifth-floor slab around column 5E finally gave way, even though the units had been shut off. The damage was irreversible. The building that should never have stood for five years had reached the end of its borrowed time.

The collapse killed 502 people and injured 937. Rescue crews arrived within minutes, but the mayor initially called off the operation, fearing the unstable wreckage would collapse further. Massive protests from families of the missing forced officials to reverse the decision, and the search continued with the structure steadied by guy cables. Korea Telecom transmitted signals every thirty minutes, hoping to trigger cellphones or pagers carried by survivors below. Despite sweltering summer heat, some of those trapped survived by drinking rainwater. Eighteen-year-old Yoo Ji-hwan was pulled out after nearly twelve days. The last survivor, nineteen-year-old store clerk Park Seung-hyun, emerged from the wreckage seventeen days after the collapse with only a few scratches. Others were not as fortunate: a man rescued after nine days reported that fellow survivors had drowned from rainwater and fire-suppression water pooling in the debris.

During interrogation, Lee Joon revealed his priorities: his chief concern, he told investigators, was not the dead but the financial damage to his company. He was convicted of criminal negligence and sentenced to ten and a half years, later reduced to seven and a half on appeal. His son Lee Han-sang, the store's CEO, received seven years for corruption and accidental homicide. Two Seocho District officials were convicted of taking bribes. The Sampoong Group ceased to exist after the Lee family pledged their entire wealth to compensate victims, a settlement that eventually encompassed 3,293 cases totaling roughly 375.8 billion won, about 300 million U.S. dollars. Lee Joon died in 2003, shortly after his release from prison.

The site of the collapse is now occupied by Acrovista, a luxury apartment complex completed in 2004. In Yangjae Citizen's Forest, a twelve-meter marble memorial designed by sculptor Kim Bong-gu stands in memory of the 502 who died. The disaster forced a national reckoning with the hidden costs of South Korea's breakneck economic development. Coming just nine months after the Seongsu Bridge collapse killed 32 people, the Sampoong catastrophe exposed systemic failures in construction oversight, building inspection, and corporate accountability. The Disaster Control Act, passed in response to both tragedies, established the framework for the safety regulations that govern South Korean construction today. The lessons were written in concrete and blood.