He was shot in 2019, and Keltner's wife said a blood transfusion gave loved ones time to say goodbye.
So now they want to give back.
The family said the drive is happening Sunday because it's also National Law Enforcement Appreciation Day.
Keltner was shot while working as a member of the U.S. Marshal's Fugitive Task Force. They were trying to serve a warrant at a Rockford motel.
"I'm just excited to see everyone in the community come together and do something great to support each other and our local law enforcement," Rebecca Keltner said. "It's been a difficult time for our family, and everything's been super hard. And it would be easy to look at the negative of everything, but I chose to turn it into a positive and try to do some good in the world."
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She said it feels good to help the community that has helped her so much. All the blood stays local.
"I know there's a lot of people sick right now that need it," Keltner said.
It all comes at a critical time, as blood shortages continue to affect the country.
"It is amazing how much support there is. Especially, you know, that he's a police officer. I like to see that," said Dale Schmidt, who donated Sunday.
There was no shortage of support in Crystal Lake Sunday -- all 250 slots were booked.
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"What's helped mitigate the pain and what's helped me get through in all of us is seeing the community rally behind us, people from near and far," the deputy's brother Luke Keltner said.
And many of Jacob Keltner's former colleagues honored his legacy by showing up to donate.
"It's hard to put into words. I can't tell you how good it makes us feel to be able to do this," Deputy Sheriff Stan Myk said. "Jake would've loved this. He would've absolutely loved this."
"Knowing that anytime, any kind of incident can happen, we can always revert back to these guys that are here with us, we always have someone to talk to, someone to lean on," Deputy Sheriff Jerry Cello said.
Everything got started at 11 a.m. at the Crystal Lake YMCA, located at 701 Manor Road, and people can come by to give blood until 5 p.m.