The two were working about 40 ft up in a lift, installing bolts to secure a rafter being held in place by a Grove TM9120 crane owned by Boise-based Inland Crane Inc., when the structure collapsed, according to the complaint. When the falling rafter hit the lift arm they were “slammed” to the ground. Coc Och died instantly, and Sontay Tsi died a few minutes later.

A third person, Craig Durant, who was co-owner of Big D, was also killed in the collapse. Nine other workers were injured. 

Attorneys representing the families of Coc Och and Sontay Tsi filed a suit earlier this month in federal court in Idaho against Big D, Inland Crane and other firms involved with the project.

Records show Boise officials approved the original hangar plans in December. However, attorneys for the two families say the owner was threatening to impose penalties if the work was not completed on schedule. 

Big D later had a second set of drawings drafted, which were not submitted to the city, according to the complaint. The modified plans had 25-30% less bracing than the approved plans, and cable-bracing connections were designed at an angle that could cause them to cut through the cables under certain conditions. 

The “serious design and engineering defects” included a lack of proper bracing, any side flange, proper cable support, X bracing through all the available bays and proper joint support of the columns and rafters, according to the complaint. 

Work proceeded with the unapproved plans using parts that had been “rushed,” “improperly and poorly welded” and were not properly sized to fit with the prefabricated portions of the structure, according to the complaint. And even when Big D submitted plan modifications to the city in January, they did not include the bracing and structural support modifications. 

Big D “disputes the allegations listed in the complaint, but we are not able to comment further on the matter as it is now the subject of pending litigation,” a company representative said via email. 

The plaintiffs say unapproved modifications were performed with "poorly welded" components (right), compared to those from the manufacturer (left). Photos courtesy Serna & Associates PLLC

Big D moved Coc Och and Sontay Tsi from another project to the hangar in an effort to finish the shell by Jan. 31, the complaint states. By Jan. 30, workers were reporting bowing beams and snapping cables and bracing, they later told police.

Jan. 31 was a windy day. According to the complaint, cranes working on nearby projects, including the Arthur high-rise in downtown Boise and the Micron semiconductor facility expansion, had stopped work that morning because of the weather. However, work on the hangar continued until the fatal collapse at about 4:54 p.m. 

A representative for Inland Crane said in a statement that the company “expresses its deepest condolences to the families and loved ones of the victims in this tragic incident.” They added that they believe the evidence demonstrates Inland and its employees are not at fault. 

An Occupational Safety and Health Administration case initiated after the collapse remains open, records show.

Coc Och and Sontay Tsi were both originally from Carcha, Guatemala. Enrique Serna, one of the attorneys representing their families, says the men had been sending money back home to their families, including Sontay Tsi’s children. Despite being far from home, both had been in daily contact with their families via video call before their deaths. 

“Now they’re feeling the void,” Serna says of their families.