'This Week' Transcript: Sen. Claire McCaskill

April 6, 2014— -- Below is the rush transcript for "This Week" on April 6, 2014 and it may contain errors.

ANNOUNCER: ABC's This Week. Rampage.

UNIDENTIFIED MALE: He came back with a gun and opened fire.

ANNOUNCER: The moment of attack, the heroes who saved lives. This morning, we're at Fort Hood with breaking details and taking on the critical questions.

Plus, culture of coverup?

MARY BARRA, CEO, GM: I don't have the complete...

UNIDENTIFIED FEMALE: That is incredibly frustrating.

ANNOUNCER: The head of GM grilled over a massive car defect linked to multiple deaths. Should you feel safe behind the wheel?

And, campaign cash...

UNIDENTIFIED FEMALE: Keep our eyes on the prize.

ANNOUNCER: The Supreme Court strikes down limits on donations. Will it protect your freedom of speech or is our democracy now for sale?

From ABC News, This Week with George Stephanopoulos begins now.

RADDATZ: Good morning. I'm Martha Raddatz in Fort Hood, Texas, a tight-knight community reeling from another horrific mass shooting this week, the second in five years.

We'll have complete coverage of the story here shortly, including the latest on the investigation.

But first, as we come on the air, breaking news in the hunt to find that missing Malaysia Air 777. We're learning that an Australian ship may have heard the pingers from flight 370's black boxes just hours ago. Just yesterday, the Chinese reported they, too, were investigating so-called acoustic events.

It's a critical time in the search. The batteries powering those pingers could die today, 30 days after the plane disappeared.

We have two reports this morning beginning with Clayton Sandell in Australia -- Clayton.

CLAYTON SANDELL, ABC NEWS CORRESPONDENT: Good morning, Martha.

That's right, after that Chinese navy ship reported hearing two pulse signals that are consistent with what you'd expect to hear from an airplane's black boxes, the Australians wanted to send their own ship to check it out.

It's called the Ocean Shield and it's carrying underwater search gear that belongs to the U.S. navy, but now that ship which is 350 miles from the Chinese vessel is staying in place, because it has its own lead to chase. They've now heard a third mysterious underwater sound.

Now keep in mind the Australians leading the search here say these are important and encouraging leads, but stress they cannot verify if any of these signals are connected in any way to Malaysia 370.

There's another development this morning, the high priority search area has shifted again, that's because of a new analysis of those last communications transmitted from the plane to a satellite now suggesting the Boeing 777 was going faster than first thought. That would put it going into the ocean very near where the Chinese picked up their signal.

Now a British ship is expected to arrive on the scene early Monday to help determine if this is something or just another false lead.

But right now it is the most promising lead in this search that has now stretched nearly a month -- Martha.

RADDATZ: Thanks, Clayton.

Well, investigators still have found no sign of the jet, they are learning lessons that could prevent another missing plane mystery like this one. Here's ABC's David Curley.

(BEGIN VIDEOTAPE)

DAVID KERLEY, ABC NEWS CORRESPONDENT: Dozens of flights, a flotilla of ships, hundreds of pairs of eyes and still not one piece of debris from the Malaysian 777 has been recovered.