A 113-page report into the cause of a partial condo collapse in Davenport, Iowa has determined that the building crumbled due to construction work that took place three days prior.

Three people — Branden Colvin Sr., 42, Ryan Hitchcock, 51 and 60-year-old Daniel Prien — perished on May 28. The Iowa Department of Health and Human Services found the men died from asphyxiation.

Approximately seven people were rescued in the hours after the collapse, which happened around 5:00 p.m. CT. Authorities amputated the leg of one resident, Quanisha “Peach” Berry, to free her from the rubble.

According to the report, the tragedy would not have occurred had “a proper shoring and construction phasing plan been implemented” during the masonry and repair work before the incident. Instead, engineers concluded that contractors removed multiple sections of bricks, causing the 116-year-old building’s western wall and areas supporting it to collapse.

White Birch Group LLC and SOCOTEC Engineering, Inc., the two firms that wrote the report, stated that construction workers did not appear to have considered that the “western wall served as a critical structural load bearing element.”

The repairs, the firms found, also did not align with customary masonry practices.

On May 25, a city inspector ordered the condo’s owner, Andrew Wold, to replace “100 linear feet of brick exterior,” according to a Davenport building permit. This week, Wold filed a lawsuit against Select Structural Engineering, the firm that inspected the structure in February.

Wold has been named as the defendant in about six lawsuits following the incident.

The city hired White Birch Group LLC and SOCOTEC Engineering, Inc within days following the collapse to determine what caused it. Hundreds of documents released by Davenport officials revealed that Wold had a history of neglecting the building.

Mayor Mike Matson expressed regret in the wake of the collapse, despite multiple warnings from experts, including one city building inspector who found that part of the south-west wall had been gradually failing in February.

Without adequate renovations, the inspector said she’d post emergency vacate orders onto the building.

Still, Matson said at a news conference, “It is a line to say it’s so unsafe you have to be kicked out of your home.

“I don’t know that anyone can anticipate a building collapsing.”