(a) It is a Class E felony for any person to assault any officer or employee of the department while performing duties as such officer or employee, or to assault any such officer or employee or a member of such officer's or employee's immediate family at any other time, if it is shown that such assault was by reason of the fact that such officer or employee had at some time performed an official duty as an officer or employee of the department with respect to any person. Any violation of this subsection