He died working with his strike team on the eastern flank of the almost 400-square-mile blaze burning in Ventura and Santa Barbara counties.
An accident review team will be looking at the situation that led to the fatality, which occurred in the Fillmore area Thursday morning.
Cal Fire officials warned the next massive blaze could start with just one spark.
Cal Fire is putting crews on standby. He was "the kind of firefighter you could rely on". Iverson joined the state firefighting department in 2009. He is survived by his wife, who is pregnant, and a 2-year-old daughter, as well as his parents and other family.
Wildfires have been a part of the California ecosystem since long before modern settlement, let alone the exurban sprawl that brings housing and development into fire-prone areas. The back burn reportedly saved dozens of homes.
"Years went by and I suppressed my fear not knowing that I would marry a fire fighter", Ashley Iverson wrote. The Ventura County medical examiner said she died of blunt force trauma with smoke inhalation and thermal injuries.
There have been seven total injuries, with three being the most serious, for the fire which began at 3:44 a.m. December 5 located four miles east of Sylmar.
"As people are asking how they can help, what we know is that they first need your prayers", the page reads. Its goal is $150,000. "The Thomas Fire has many unprecedented conditions and complexities that challenge the already demanding job of fire suppression".
Approximately 95,000 residents thus far have been evacuated, Cal Fire said, and more than 1,000 structures have been damaged.
Firefighters have taken advantage of a two-day lull in winds to increase fire containment to 30 percent.
According to KTLA: "Officials are anticipating that the massive Thomas Fire burning in Santa Barbara and Ventura counties won't reach full containment until January 7 - more than a month after it was sparked, Cal Fire said Friday".