Dan began his career in law enforcement with the NYPD in 1995. He joined the ranks of the Secret Service in 1999 as a special agent where he was assigned to investigate financial crimes. In 2006, Dan entered into duty with the elite Presidential Protective Division in the administration of President George W. Bush. He remained on protective duty during the change in administration to President Barack Obama. He resigned from the Secret Service in 2011 to run for a senate seat in Maryland.