Geenen submitted his two-sentence letter of resignation to Mayor Mike Thoms on Nov. 19, which was notarized by a Hennepin County, Minn., notary.
Minneapolis is the largest city in Hennepin County. It is unknown why Geenen was in Minnesota at the time.
"I hearby resign from my office effective immediately," Geenen wrote. "It has been (an) honor to serve the city of Rock Island."
Geenen, 40, was terminated from the Doris & Victor Day Foundation Nov. 4 after admitting to a member of the board of directors that he allegedly embezzled an amount close to $40,000 from the nonprofit group.
Kai Swanson, secretary for the Day Foundation board of directors, said the board held an emergency meeting later the same day and "voted unanimously to terminate Mr. Geenen's employment effective immediately."
A criminal complaint was initially filed with the Rock Island Police Department, but was referred to the sheriff's department to avoid conflict of interest considering Geenen’s role as a city alderman.
Rock Island County Sheriff Gerry Bustos said a criminal investigation was opened Nov. 9 into theft from the Day Foundation but would not name Geenen as a suspect.
Geenen was the only paid employee of the Day Foundation. The foundation's 2020 tax return lists his salary as $81,100 at the time. As an alderman, Geenen also was paid an annual stipend of $6,000.
"We want to thank Alderman Dave Geenen for his service to the city of Rock Island and wish him well in his future endeavors," Thoms said during Monday night's council meeting. "He's done well for the city and worked hard in representing the 7th Ward."
Pursuant to Illinois statute, Thoms said he must appoint a "qualified person to fill this vacancy within 60 days."
Once an appointment has been made, City Council members will have 30 days to "act on the appointment," Thoms said. The appointee will hold the seat until the next election in April 2023. In that election, candidates would be running for a two-year term to get back into the cycle with the other council seats.
Thoms is asking for anyone who is interested in serving as 7th Ward Alderman to submit a letter of interest to him by Friday, Dec. 3, at firstname.lastname@example.org or by mail to City Hall, 1528 3rd Ave., Rock Island, 61201.