CHICAGO—Stephen Hearn was in a celebratory mood yesterday, but remained conscious of the obligation he and his partners had just assumed. The president and CEO of the Chicago-based The Hearn Company, along with The Lynd Company and Mount Kellett Capital Management LP, had just completed their purchase from Deutsche Bank AG of the 900,000-square-foot office sector and 710-car parking facility of the John Hancock Center, perhaps Chicago's most notable building.

“A responsibility is the word I've been using to describe this,” Hearn said. “It's a chance that only comes along once every 20 or 30 years to make a difference in an iconic property. When we bought 55 West Monroe [in 2011], the truth is nobody except those in the building cared all that much who bought it. I think the John Hancock Center is different. It's part of the fabric of the city of Chicago.”

The purchase includes the offices on floors 13 through 41, the parking spaces on floors 4 through 12, and common areas such as the plaza, concourse and the entries and lobbies on Chestnut and Delaware. Condominiums occupy many of the upper floors in the 3.1-million-square-foot, 100-story tower, and Deutsche Bank AG had earlier sold off other remaining sections. The financial terms of this latest transaction were not disclosed.