Are they dead, or not?

What does it mean when the BBC puts quotation marks around the word "killed" in this headline?

Three al-Qaeda members 'killed'

Three al-Qaeda members were among those killed by a US missile strike last week in Pakistan, security officials say.

Among them was Midhat Mursi, an explosives expert who had a $5m reward offered for his capture.

If they doubt that the people who were killed were actually terrorists, shouldn't they put "al-Qaeda members" within quotation marks? Do they doubt that they were killed? Strange.