Washington (CNN) Embattled Rep. Aaron Schock announced Tuesday he would resign his seat at the end of the month, in the wake of a congressional ethics investigation into reports that he used taxpayer money to fund lavish trips and events .

In a statement, he said he was stepping down "with a heavy heart," having given his constituents "my all over the last six years."

"But the constant questions over the last six weeks have proven a great distraction that has made it too difficult for me to serve the people of the 18th District with the high standards that they deserve and which I have set for myself," he added.

Politico first reported on Tuesday afternoon that Schock would step down. The news marks the end of an embarrassing chapter for the former GOP rising star known for his Instagram account and a memorable shirtless appearance in a feature in Men's Health magazine.

Republicans close to Schock have said the biggest questions about his finances involve mileage reimbursements from a car paid by for by his campaign account. A Schock spokesman said Tuesday that the congressman had paid the government back for all of his official mileage, but the exact amount was unclear.

"In an effort to remove any questions, and out of an abundance of caution, Congressman Schock has reimbursed all monies received for official mileage since his election to Congress," the spokesman said.

The four-term Republican was scheduled to attend a St. Patrick's Day event in Peoria on Tuesday, but didn't show — and the news of the congressman's abrupt resignation on Tuesday afternoon took at least some staff members in his Washington office by surprise, according to a person close to the office.

And Rep. Patrick McHenry, the GOP chief deputy whip, indicated Schock had not told his fellow leadership members of his plans to resign. McHenry told reporters he had not talked with Schock about his decision, but praised him and called it "a real loss."

"I think Aaron is a very intelligent person - he has had a great career in public service from his time on the school board, his time in the state House to his time in Congress so I think it's a real loss. I think it's a real loss," he said.

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Pressed about the multiple stories about improper travel/campaign spending, McHenry said, "I know none of the details."

But House Speaker John Boehner issued a statement shortly after the news broke praising Schock for deciding to step down.

"With this decision, Rep. Schock has put the best interests of his constituents and the House first," Boehner said. "I appreciate Aaron's years of service, and I wish him well in the future."

Within minutes of Schock's announcement, national Democrats pounced, with Democratic Congressional Campaign Committee spokesman Matt Thornton suggesting it was the latest example of disarray within Boehner's caucus.

"Fewer than 100 days in, Speaker Boehner has already seen his Speakership challenged, his caucus defiantly reject him time and again, some of his closest colleagues retire rather than watch their reputations dragged down by the gridlock and dysfunction, and now the second member of his caucus has resigned amid ethics scandal," Thornton said in a statement, a reference to Long Island Rep. Michael Grimm, who resigned this year after pleading guilty to felony tax evasion charges.

"Speaker Boehner's Republican caucus is more like Animal House, and the American people deserve better," Thornton added.

Illinois Gov. Bruce Rauner must set an election date within five days of Schock's resignation, at the end of the month, and the election must occur within 115 days of that, or sometime before the end of July.

Democrats have little chance of taking the deep-red seat, but Republican candidates were already surfacing Thursday afternoon. According to a congressional source, Illinois state Sen. Darin LaHood — the son of former Obama Transportation Secretary Ray LaHood — is planning to run.

LaHood opted out of challenging Schock before and, according to the source, has been laying low watching the scandal plays out. He is expected to announce his candidacy on Wednesday, the source said.

Photos: Politicians in hot water U.S. Rep. Chaka Fattah was convicted on federal corruption charges on Tuesday, June 21. The Philadelphia Democrat was tied to a host of campaign finance schemes, according to the Department of Justice. Hide Caption 1 of 12 Photos: Politicians in hot water Former Speaker of the House Dennis Hastert was sentenced to 15 months in prison and ordered to pay $250,000 to a victims' fund in April after a hush-money case revealed he was being accused of sexually abusing young boys as a teacher in Illinois. Hide Caption 2 of 12 Photos: Politicians in hot water Former Virginia Gov. Bob McDonnell arrives at his corruption trial in Richmond, Virginia, in September 2015. A jury convicted McDonnell and his wife, Maureen, derailing the political ambitions of the one-time rising star in the Republican Party. McDonnell, who was sentenced to two years in prison, has asked the Supreme Court to reverse his conviction. The high court heard his challenge in April. Hide Caption 3 of 12 Photos: Politicians in hot water U.S. Sen. Robert Menendez, a New Jersey Democrat, was indicted on corruption charges in April 2015. Federal prosecutors have accused Menendez of using his Senate office to push the business interests of a friend and donor in exchange for gifts. The senator has pleaded not guilty to the charges and vehemently asserts his innocence. Hide Caption 4 of 12 Photos: Politicians in hot water U.S. Rep. Vance McAllister asked for forgiveness from God, his family and his constituents after a newspaper published what it said was surveillance video showing the married Louisiana Republican making out with a female staffer. His term ended in 2015. Hide Caption 5 of 12 Photos: Politicians in hot water Former U.S. Rep. Jesse Jackson Jr. and his wife, Sandra, arrive at federal court in Washington for sentencing in August 2013. Jackson, a Democrat from Illinois, was sentenced to 30 months in prison for improper use of campaign funds, while his wife got 12 months for filing false tax returns. Hide Caption 6 of 12 Photos: Politicians in hot water In 2012, former Illinois Gov. Rod Blagojevich was sentenced to 14 years in prison after being convicted of 18 criminal counts, including trying to sell the appointment to fill the U.S. Senate seat vacated by Barack Obama. Hide Caption 7 of 12 Photos: Politicians in hot water Lewis "Scooter" Libby, former chief of staff for Vice President Dick Cheney, was convicted in 2007 of obstructing a federal investigation into who revealed the identity of CIA agent Valerie Plame Wilson. He was sentenced to 30 months in prison and fined $250,000, but former President George W. Bush commuted his sentence. Hide Caption 8 of 12 Photos: Politicians in hot water Former U.S. Rep. William Jefferson was sentenced to 13 years in prison in 2009 after being convicted of 11 counts of corruption related to using his office to solicit bribes. The Louisiana Democrat was also ordered to forfeit $470,000. Hide Caption 9 of 12 Photos: Politicians in hot water Former U.S. Rep. Bob Ney, a Republican from Ohio, was sentenced to 30 months in prison in 2007 after being convicted of conspiracy to commit fraud and making false statements to investigators. Hide Caption 10 of 12 Photos: Politicians in hot water U.S. Rep. James Traficant Jr., D-Ohio, spent seven years in prison after being convicted of bribery and corruption and tax evasion charges in 2002. Hide Caption 11 of 12 Photos: Politicians in hot water Former U.S. Rep. Randy "Duke" Cunningham, R-California, was sentenced to eight years in prison in 2006 after he was convicted of collecting $2.4 million in homes, yachts, antique furnishings and other bribes on a scale unparalleled in the history of Congress. Hide Caption 12 of 12

The scandal surrounding the Illinois Republican's spending practices has ballooned since a Washington Post profile of his whimsically decorated office published last month raised initial questions about his finances.

Schock ended up paying back the government the $40,000 it cost to redecorate his office in the style of the popular PBS drama "Downton Abbey," but the controversy didn't stop there. The Illinois Republican later came under scrutiny for flights on private jets — including planes owned by key donors — concert tickets and other entertainment expenses. He's also under fire for lapses in reporting some of his expenses.

Most recently, The Associated Press reported on an array of Schock's business dealings that involved his political contributors. A number of Schock's associates had been contacted by investigators with the Office of Congressional Ethics, sources tell CNN, though the OCE did not respond to a request for comment.

With Schock's resignation, the Congressional ethics investigation will go away. The ethics committee has jurisdiction over sitting members of Congress. But any other potential probes, including a criminal case, would continue.

A constituent visiting D.C. on Tuesday to meet with Schock's staff about agriculture issues said that he was "surprised" and "sad" that the congressman had resigned.

"I'm very surprised that that happened. I'm sad that it happened, especially the way that it did," Ted Mottaz, a resident of Elmwood, Illinois, told CNN just outside of Schock's Capitol Hill office.

Schock, he said, had done a good job representing his district and his group's interests.

Local news back in the district had carried coverage of the scandal, but Mottaz said he hadn't expected the congressman's spending issues to result in his resignation.

Still, Schock's office made a "questionable statement."

"When I first went into the office I was just — I was flabbergasted at the size. And I was flabbergasted the next time I came back, how it was decorated," Mottaz said.

"And then today, we were in the main part, and it was beautiful, but I'm not sure — I'm not sure if it's really that bad, but it's still kind of a questionable statement that makes," Mottaz added.

CORRECTION: An earlier version of this story misstated when Rep. Michael Grimm resigned.



