Anwar al-Awlaki's Last Words Cut Short?

Sept. 30, 2011 — -- Just days before al Qaeda cleric Anwar al-Awlaki was killed in what Yemen officials said was an airstrike in their country overnight, an al Qaeda magazine promised a provocative message from the American-born radical was still to come.

The latest issue of "Inspire", an al Qaeda magazine believed to be produced by the Yemen-based al Qaeda affiliate al Qaeda in the Arabian Peninsula (AQAP), featured a large advertisement for an upcoming article apparently written by al-Awlaki called "Targeting the Populations of Countries That Are at War With the Muslims". Al-Awlaki was a prominent member of AQAP.

The promotional ad uses as its background a picture of New York City's Grand Central Terminal, perhaps a clue, U.S. security officials said in a law enforcement bulletin, that it's "an allusion to the continued interest of extremists in general of targeting New York City for terrorist attacks."

Today NYPD Commissioner Ray Kelly went further, saying Samir Khan, an American-born AQAP jihadist who publishes the magazine, had "identified Grand Central [Terminal] as a target."

Khan was killed in the same air strike that took out al-Awlaki, U.S. officials said.

READ: Anwar al-Awlaki Killed: Officials in Yemen Confirm Al Qaeda Cleric Dead

While it is unclear if al-Awlaki managed to complete the piece before his death, it would hardly be the first time the New Mexico-born cleric has justified and urged individuals to launch terror attacks against U.S. civilian targets.

American officials said al-Awlaki's online sermons may have served as inspiration for more than a dozen terror plots against the homeland including the Fort Hood Massacre and the failed Christmas Day bombing.

READ: Officials Thought They Might Kill al-Awlaki on 9/11 Anniversary

Due to his ability to inspire so-called lone-wolf terrorists in the U.S., several U.S. officials have said al-Awlaki was more dangerous than even the late al Qaeda founder Osama bin Laden.

"If you look at his terrorist resume for the things he's been involved with, you can really call him the most dangerous man in the world," Lt. Kevin Yorke of the NYPD's Intelligence Division said in November 2010.

Earlier this year, America's chief counter-terrorism official Michael Leiter called him and AQAP "probably the most significant risk to the U.S. homeland."

ABC News' Martha Raddatz and Atta Nasser contributed to this report.