Transcript for David Cameron Addresses New ISIS Video
the latest horror from the terrorist army known as Isis. The vic this time a british aid worker by the name of David Haines. He had a wife and children. Isis posting the horrific video Saturday and the condemnation was immediate and global. President Obama who is in the middle of trying to build a coalition to fight Isis calling this third public execution of a westerner, quote, barbaric. We have team coverage this morning and start with ABC's chief investigative correspondent Brian Ross. Brian, good G to you, sir. Reporter: Good morning, british security officials are in emergency session this morning with the prime minister calling the beheading of british aid worker David Haines pure evil. The victim was british. But the brutal video message was clearly aimed at the united States. It was the same desert setting, the same masked executioner with a british accent and the same horror. 44-year-old David Haines was forced to kneel in an Orange jumpsuit and read a script that laid the blame for his execution on prime minister David Cameron. Prime minister, what are your thoughts about the hostage. Reporter: Overnight the prime minister returned to 10 downing treat for the series of emergency meetings to be held today. In a statement he released on Twitter Cameron said we will do everything in our power to hunt down these murders and ensure they face justice, however long it takes." Haines was the married father of two who served in the british military and went there as a civilian with a French aid group. He was no stranger to the world's hot spots. This was him 11 years ago when he served in Croatia. Many people want to return but don't know who to turn to. Reporter: Since his kidnapping a year and a half ago his family has tried to find a way to gain his release. His teenage daughter posted "B ed but no ran some would be paid. The U.S. Has been conducting drone flights over raqqah. So far without success. One senior official told ABC news this latest execution out in the open during the day is a sign that Isis still feels it can carry out its medieval acts with impunity and U.S. Officials say it still holds two young American aid workers and two more british citizen, one of whom appeared in this latest video described as the in ex-victim. So four more families in anguish this morning. Brian, thank you. Let's go to Washington now and our chief global affairs correspondent Martha Raddatz. Martha, good morning. Is it possible that this was potentially strategically unwise move? The white house is trying to recruit. So would that make it easier? It enrages the United States. It enrages the british. I think one of the reasons they do this is try to recruit more fighters. Their jihad attracts peep. We do not know why it is resonating so well but it does attract people so try to paint themselves as the winners. Look, we just killed a british citizen. We just killed two American citizens and they think that will resonate with the kind of people who are attracted to them. That leads me to the question I want to ask this morning. As we prepare to expand our military campaign there are some critics at home who argue that Isis, it's been not a threat to the homeland. What is your view on that. Well, you know this all started with defense secretary chuck Hagel who said it was an imminent threat. I think what you hear from the administration and others in the counterterrorism world is that it is a potential threat. But they want to stop that potential threat to the homeland. They don't think there are any specific targets in the homeland. Certainly they are a threat to westerners who are in the area as we have seen from the executions and they would like to hit western targets but most people don't think they are capable of going beyond that and hitting the homeland at this time but I'll tell you, Dan, the big worry is those lone wolf, someone down in the basement who is plotting an attack. That has been the worry for some time now. Martha, thank you. Martha will be hosting "This week" later this morning and she'll have much more on this breaking story including an interview with Denis Mcdonough, chief of staff, later this morning on "This week" right here on ABC.
This transcript has been automatically generated and may not be 100% accurate.