The 38-year-old man from Healdsburg was arrested Friday morning at the agency's Howard Forest station in Mendocino County.
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"I'm still processing this but he doesn't live here, nor has he," said the suspect's estranged wife.
The estranged wife of a 38-year-old Cal Fire Apparatus engineer, wants to stay anonymous but says she's speechless about her husband's arrest for suspicion of felony arson. ABC7 News is not identifying the firefighter until he's been officially charged.
"I don't think anyone will have any idea that this had been happening, I'm 100 percent in shock," she said.
The department suspects the firefighter of causing five brush fires in Sonoma County this summer while he was off duty, including, the Alexander Fire on Aug. 15, the Windsor River Road Fire on Sept. 8, the Geysers Fire on Sept. 12 and the Geyser and Kinley Fires on Sept. 14.
Cal Fire says, all five brush fires burned less than an acre of wildland due to the quick action of residents and firefighters.
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Cal Fire's Director, Chief Joe Tyler said in a statement, "I am appalled to learn one of our employees would violate the public's trust and attempt to tarnish the tireless work of the 12,000 women and men of Cal Fire."
Tyler says information from the public helped make an arrest.
"It's a tough pill for all of us," said Sonoma County Fire District Division Chief Cyndi Foreman.
Local firefighters, some who responded to the fires over the summer, are saddened by the news.
"When you read the press release and understand someone out in the community is supposed to be protecting us they're actually putting us in harm's way, that's hard to read," Foreman said.
The suspect will be booked into the Sonoma County Jail on suspicion of arson to forest land, he's scheduled to be arraigned next week.
The agency's law enforcement officers have arrested 91 suspected arsonists this year as of Sept. 1 and 923 since 2016. For more information, visit the Cal Fire website here.