Abstract: At 3:22 a.m. on April 4, 2023, an employer was notified of an residential fire and dispatched a compliment of units. When Engine 75 (E75) arrived, they pulled up to the fire, just past the fire building. E75 took a hose line to protect the front door of the residence and was met with "heavy fire at the front door," and pulled out. E75 informed the Battalion Chief 22 that there was "a lot of fire in 12017." E75 then protected exposures with a two-and-a-half-inch hose line to the alley way. The E75 officer and Firefighter #1 grabbed an inch and three-quarter hose, went through the front door, entered through the first floor to the rear stairway, and went directly to the attic. The E75 officer and Firefighter #1 operated in the attic until conditions deteriorated, and the E75 officer determined that they should leave the attic. The E75 officer told Firefighter #1 they were leaving the attic, and Firefighter #1 acknowledged. The E75 officer turned around to exit the attic and go down the rear stair well, got to the bottom, and realized Firefighter #1 was not with him. The E75 officer pulled on the hose line, but it wouldn't move and noted he was low on air. The E75 officer saw a Battalion Chief and told him that Firefighter #1 did not come down from the attic with him and that he was low on air. A mayday was called. Firefighters located Firefighter #1 in the attic, where he was unresponsive. A significant effort was required to remove Firefighter #1 from the attic and residence where he was transferred to EMS for lifesaving efforts. Lifesaving efforts continued, and he was transported to a hospital. Firefighter #1 died from carbon monoxide toxicity due to inhalation of smoke and soot. Other significant conditions contributing to the death were thermal injuries and hypertensive-arteriosclerotic cardiovascular disease.