Flahive, who had been a firefighter since 1989, died this week, apparently from the West Nile virus.
His family of colleagues at his Northwest Side firehouse near Milwaukee and Laramie cannot believe he is gone.
Flahive started feeling flu-like symptoms at work. Fire department officials say about two weeks ago, Flahive was vacationing in Wisconsin when a mosquito bit him in the neck.
The 58-year-old lieutenant went to get checked out and was diagnosed with West Nile virus. He soon went into a coma and suffered severe brain damage.
His colleagues say even though they got the news that Flahive wasn't doing well, no one expected the disease to take his life.
"When you see a guy like Tommy, who is big as a house and strong as an ox, being brought down by something as small as a mosquito bite, it is shocking, and quite frankly, heart-breaking to everybody on this job," said Tom Ryan, president of Chicago Firefighters Union Local 2.
"It takes time to comprehend and absorb that even after his death, still for some of us it hasn't sunk in. It's not going to sink in until we see him missing from his chair, the chair he often sat in, the Flahive chair," Mark Nielsen of the Chicago Fire Department.
Bunting was raised in Flahive's honor at his firehouse at 8 a.m. There was also a small ceremony, including a moment of silence.
His funeral services are set for Monday.
Flahive's family, which includes his wife and three adult children, plans to donate parts his body for researching the West Nile virus.