Schock, 33, is accused of congressional and campaign misspending. The investigation began after his office was decorated to look like TV show "Downton' Abbey".
His father, Dr. Richard Schock, spoke to ABC7 Chicago outside his Peoria home on Wednesday morning. He said he fears that his son could face prison for what he calls "paperwork problems."
"If they're going to convict him on paperwork, then they're going to convict him. That's their privilege," Dr. Richard Schock said. "They're out to get him and they're making issues out of things that really shouldn't be issues."
WATCH the FULL Interview with Dr. Schock
Dr. Richard Schock spoke with his son Tuesday after the resignation was announced. He called the congressman "broken" but a "fighter."
His father said the congressman is stepping down to spare supporters from a potential court case.
"He's a fighter, but it's not about him anymore. It's about me and a lot of his friends, and a lot of his supporters, and they're all being attacked right now," Dr. Schock said. "He doesn't want to go on. He doesn't want to bring them into court and have to be subpoenaed and everything."
Schock plans to resign on March 31, 2015.
His stepping down will end a House Ethics investigation of how campaign and taxpayer funds were spent, including recent disclosures that he billed taxpayers for 170,000 miles on a car driven by Schock and owned by his campaign, even though the SUV only had been driven 80,000 miles, according to the odometer.
That SUV was parked in his father's driveway Wednesday. A Schock spokesperson said Tuesday night that all mileage expense reimbursements have now been repaid to the government.
A criminal investigation is still possible. On Wednesday, law enforcement sources said that while the FBI has not launched an investigation, authorities are "monitoring" the matter.
Long before Schock got to Congress and found fame on Instagram and the cover of "Men's Health," he was known in Peoria as an enterprising young man. He started his first business as a teenager and won a spot on the local school board at the age of 19. Then he went on to Springfield, Ill., and soon after was in Washington, D.C.
"He's had a good run. He's done a lot of good. He's helped a lot of people," Dr. Richard Schock said.