Cook County Deputy Richard O'Brien died Sunday as a result of coronavirus complications. He was 53.
The 25-year veteran of the sheriff's office is being remembered by his peers as "a highly motivated and dedicated professional," the sheriff's office said.
O'Brien was already battling heart problems and stage one leukemia when he came down with COVID-19.
O'Brien leaves behind a wife, Cindi, and three children.
The Cook County Sheriff's Office said O'Brien's death will be considered in the line of duty and means his family will have continuing financial support.
Cindi O'Brien shared details about her husband's health battle with ABC7 last week.
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The last time Cindi spoke to her husband was right before he was put on a ventilator.
"He called and he said 'I love you, and I promise I'll come back to you,'" she recalled.
O'Brien served in the Cook County Sheriff's Department for more than 25 years, most recently in the Skokie courthouse. That courthouse is where his family believes he contracted the coronavirus.
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"I actually asked him not to go to work, and he just couldn't not," Cindi said last week. "He's like, 'I can't let leukemia win.'"
The sheriff's office released a statement Sunday, saying O'Brien "earned the respect of his peers and supervisors for always asking to be assigned to the frontline and for going the extra mile."