Republican U.S. Congressman Aaron Schock just quit Congress. And everyone’s trying to figure out why. Here’s your answer.

Aaron Schock’s resignation this afternoon came as a surprise, even to some of the most ardent political prognosticators. The Illinois Congressman has been the target of investigation by watchdogs and journalists for at least the past six weeks, and likely longer.

But in breaking the news today, Politico offered this stunning insight into how the 33-year old moderate Republican managed his campaign and congressional finances, and it’s not pretty.

“Schock billed the federal government and his campaign for logging roughly 170,000 miles on his personal car between January 2010 and July 2014,” a three-person team at Politico reports this afternoon. “But when he sold that Chevrolet Tahoe in July 2014, it had only roughly 80,000 miles on the odometer, according to public records obtained by POLITICO under Illinois open records laws. The documents, in other words, indicate he was reimbursed for 90,000 miles more than his car was ever driven.”

The article details the ins and outs of the purchase, raising more questions.Â

But there’s more.

“Separately, on a campaign finance document, Schock labeled the cost of a November flight on a private plane as a software purchase. He has failed to report trips abroad, as required. And he held a fundraiser at a golf course without reporting paying for its use.”

In an interview with POLITICO last week in Peoria, Schock could not say with certainty that he had not broken the law. â€œI certainly hope not,â€ Schock said.

And more.

The Office of Congressional Ethics opened an investigation of the lawmaker on Feb. 28 and has begun contacting his associates about appearing before the independent panel behind closed doors. The OCE probe â€”and any potential Ethics Committee investigation â€”will disappear with Schockâ€™s resignation. However, federal law enforcement could still look into Schockâ€™s actions.

But that one Politico report ignores the growing questions about Schock’s full-time photographer, paid for with your tax dollars.

“Jonathon Link, Schockâ€™s full time personal photographer, started September 1 and was paid $4,166 for that month, which translates to an annual salary of about $50,000,” Blue Nation Review reported in an exclusive article two weeks ago.

“In the final three months of the year, he was paid $17,500, which translates to an annual salary of about $70,000. In addition to his congressional salary, Linkâ€™s photography studio was paid more than $29,000 during the final three months of the year for ‘Web Dev Hst, Email and Rltd Serv.’ Schockâ€™s office also paid ‘Web Dev Hst, Email and Rltd Serv’ through Fireside21â€”a company that charges just a few hundred dollars per month and actually specializes in web development, hosting, email, and related services for Congressional offices. Was Link double-dipping?”

Blue Nation Review adds more fuel to the Schock fire, with this conclusion:

“Overall, Schockâ€™s payroll surged from $172,000 in the third quarter of 2014 to more than $300,000 in the fourth quarter, during which the House nearly shut down the government and failed to act on priorities like immigration reform. Three weeks later, Schock went on MSNBC to decry a proposed minimum wage increase as ‘artificially raising the cost of labor.'”

So now the question becomes, not why did he resign, but why didn’t he resign sooner?

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Image via Aaron Schock’s Instagram account, some photos likely paid for with your tax dollars.