From the criminal complaint for United States v. Jared Lee Lougher, I learn of a new federal statute, 18 U.S.C. 351(c), which provides:

(a) Whoever kills any individual who is a Member of Congress or a Member-of-Congress-elect, a member of the executive branch of the Government who is the head, or a person nominated to be head during the pendency of such nomination, of a department listed in section 101 of title 5 or the second ranking official in such department, the Director (or a person nominated to be Director during the pendency of such nomination) or Deputy Director of Central Intelligence, a major Presidential or Vice Presidential candidate (as defined in section 3056 of this title), or a Justice of the United States, as defined in section 451 of title 28, or a person nominated to be a Justice of the United States, during the pendency of such nomination, shall be punished as provided by sections 1111 and 1112 of this title.

…

(c) Whoever attempts to kill or kidnap any individual designated in subsection (a) of this section shall be punished by imprisonment for any term of years or for life.

I didn’t realize that a crime against certain types of government officials warranted a different penalty.

Update: Professor Magliocca posts an answer to my question here:

The shooting of Judge Roll and Congresswoman Giffords raises an interesting point about federal jurisdiction.  It seems obvious that this attack would be a federal crime, but that is a recent development.  Until the 1960s, the assassination of a federal official was treated as ordinary state-law murder unless it happened in Washington DC or in a federal territory. The most famous example is Lee Harvey Oswald.  Killing the President in Texas was not a federal offense in 1963, just as it wasn’t in 1901 when Leon Czolgolz shot William McKinley in Buffalo and was convicted of murder in New York.  Indeed, this is why Oswald was being held in the local Dallas jail that made it so easy for Jack Ruby to do what he did.