They say they tracked Michael Russell's excessive downloading activity to his home address where he lives with his wife.
His next-door neighbor, Jason Dominguez, saw the arrest. He told ABC7 News, "I woke up in the morning, there were just a lot of cops on the street and that's not normal. It's a pretty quiet neighborhood. Nice area."
The district attorney says there's no evidence the 74-year-old doctor committed any crimes against his patients or minors.
Russell specializes in internal medicine. A receptionist said Russell was not in the office because he retired suddenly last week.
Russell posted $150,000 bail. He's scheduled to be arraigned on March 2 and he's facing a maximum of five years in prison.