The two victims reportedly helped a woman escape the fire before they died.
The medical examiner said that the official cause of death for the two men was carbon monoxide intoxication and smoke inhalation.
The cause of the fire is still unknown, though investigators are analyzing some of the electrical appliances in the unit.
Plywood marks the floors where the fire started and spread and where John Fasula Fr. and a colleague were overcome by the choking smoke.
Fasula was a longtime maintenance manager for the CTA, but he was in the building Tuesady working for a cable company, along with colleague Jameel Johnson.
The men reportedly sent an 81-year-old woman down to safety in an elevator before trying to fight the fire with an extinguisher.
"In my heart is sorrow, sorrow that i feel for those people," said building resident Fredrinia Adair.
As the fire burned, residents on lower floors evacuated, but those who encountered smoke in hallways and stairwells were forced back into their units and even onto balconies.
As precarious as the scene looked, they were in the safest spot to be.
"Each apartment is a compartment," said Chicago Fire Department District Chief Joe Roccasalva. "So even if the fire is in the apartment next door, you're safe in your apartment."
Officials say high-rise fire deaths usually occur in smoke-filled hallways and stairwells.
That was certainly the case in October 2003 when six people died in a stairwell after the county building caught fire.
"I've been in high-rise fires where you look up, and the fire is raging in one apartment, and there's a person standing in the window next to the apartment perfectly safe," Roccasalva said.
The county building fire prompted a new ordinance requiring high-rises to have elevators that go to the bottom floor when there's a fire, as well as an intercom system for firefighters to communicate with residents.
Buildings built before 1975, including the one that caught fire Tuesday, have been given time to make those upgrades, but patience appears to be running out.
"I'm hearing it from the city," said Tom Skweres, Apartment Building Owners and Managers Association. "I'm hearing it from the press conferences that the mayor has had, from the Chicago Fire Department, and other members in our association, they're not going to push it back,"
The deadline for those older buildings to upgrade their elevators and intercom systems has already been pushed back twice by the City Council.
The deadline is currently January 1, 2015 and applies to more than 700 buildings over 80 feet in the city.