CHICAGO (CBS) — In his final speech on the House floor, embattled Congressman Aaron Schock apologized for letting down his constituents, and vowed to “work tirelessly to make it up” to them.

Schock, 33, has announced he is resigning from Congress at the end of the month, following a series of revelations about possible misuse of public and campaign funds, from a Downton Abbey-themed office on Capitol Hill, to

In a farewell speech at the Capitol on Thursday, Schock only vaguely referenced the controversies that forced him to step down.

“I believe that, through life’s struggles, we learn from our mistakes, and we learn more about ourselves, and I know that this is not the end of a story, but rather the beginning of a new chapter,” he said.

He also offered some words of contrition for his constituents and supporters.

“I was never more excited than the day I walked into this chamber six years ago. I leave here with sadness and humility. For those whom I’ve let down, I will work tirelessly to make it up to you,” he said.

The congressman also expressed thanks to his office staff.

“I’m proud of the good work that my team has delivered to the tens of thousands of constituents who’ve turned to our office for their time in need. My staff delivered for me, because they delivered for you every day, 24/7,” he said.

Federal prosecutors in Springfield have opened an investigation into Schock’s activities, and have convened a grand jury to begin interviewing witnesses next month.

Over the past several weeks, Schock has been besieged by questions about his use of taxpayer dollars and campaign cash.

Last month, a photo of a $40,000 “Downton Abbey” redo of his Capitol Hill office led to an ethics charge by an independent group.

That was followed by revelations that he billed taxpayers $1,200 for a charter flight to a Bears game at Soldier Field, which he repaid once word of it got out. But there was another $14,000 in private flights last fall on top of $40,000 worth of travel on planes owned by campaign donors.

Earlier this month, Schock defended a recent trip to New York last September, connected to a visit by the prime minister of India. Schock brought along ten staffers, all on the taxpayer dime, and he said he was glad his staff could be part of an historic event. He said the trip was official business.

Schock also has faced questions about a shell company linked to the him. The company paid a political donor $750,000 last year to purchase a warehouse in Peoria, and then took out a $600,000 mortgage from a local bank run by other donors.

Donors also built, sold, and financed a home Schock owned in suburban Peoria, and were involved in the sale of a Peoria apartment complex in which he invests.