Why save the American journalist in Yemen failed?

A senior US official said the US special force tried to rescue American journalist who was captured by al-Qaeda in Yemen because the intelligence confirmed the possibility of death at any moment, but it was during the monitoring force approached the insurgent hideout.
And was killed in a failed operation at dawn on Saturday photojournalist Luke Somers (33 years old) and the South African hostage Pierre Korki, a day before the deadline supposed to release him.
The senior US official revealed important details, saying "indicators have reached us that they are going to kill Summers, perhaps as early as the next day."
"We either had to move immediately and risk and either let the deadline pass. We were not ready to do so."
He added, referring to al-Qaeda militants "have said they Saadmonh within 72 hours, but we believe, and Ouseltna indicators through a variety of sources of information we have, that the deadline approached, we believe that they are preparing to kill him Saturday morning Ptoukatna, this is moved reason as soon as possible." .
US officials said that Obama and Defense Secretary Chuck Hagel agreed to try to rescue the bold Friday morning Washington time that the commandos began to move after a few hours.
It was made known to Hegel on the developments of the process in his plane while he was on his way to Afghanistan.
Special Forces and flew about five o'clock on Friday night, Washington time (I am Yemen) Osprey aircraft, has been lowered to 10 km from the place of the hostage-taking in Shabwa province, southeastern Yemen.
Special Force and headed to Al-Qaeda hideout walk, but hopes to move secretly under the cover of darkness to carry out the rescue faded when it was discovered ordered about 100 meters from the al-Qaeda fighters complex.
A senior defense official, who was accompanied by Hegel in Kabul "and said what we know that when he approached the attacking force of compound fighters, lost the element of surprise."
"We have lost the element of surprise when a clash broke out, and we believe that this is the time where he was killed (the hostages)."
He spent one of the hostages - it was unclear which of them - while he was on the way to the USS McCain Island, the US Navy, while the other was killed during surgery aboard the ship.
He said Vice President Joe Biden, in a speech in Washington that Luke Summers "was killed during the second attempt (for editing). We were on the verge of doing so."
The Pentagon confirmed Thursday that the United States has tried in November edit many of the hostages, including American Luke Summers, but the soldiers were unable to find their place.