From the Connecticut Post:
The two firefighters were killed in what was supposed to be a routine house fire. Fellow firefighters have speculated that they may have run out of oxygen while checking for fire remnants on the third floor.
Smoke inhalation has been ruled the cause of death for the 49-year-old Baik. The state medical examiner's office also determined he had coronary artery disease that contributed to his death. A preliminary autopsy on the 40-year-old Velasquez was inconclusive, so more tests will be conducted.
The third-floor apartment where they lost their lives was not a certified living space and had likely not been inspected by fire officials in many years, because no permits were ever issued to convert the structure to a three-family house.
Records at both the city's Building Department and Tax Assessor's Office show the three-story structure at 39-41 Elmwood Ave. was built as a two-family house in 1909.