According to the news item, the bomber was disguised as

Pakistan’s Interior Minister Rehman Malik has blamed a lapse in security for a deadly explosion detonated by a suicide bomber at a United Nations compound in the Pakistani capital Islamabad. (3) Mr. Malik said the bomber had been dressed as a member of the security forces and was allowed into the World Food Program compound when he asked to use the toilet. Five WFP employees were killed in the blast and a number of people injured. (4)No group has said it carried out the attack, but Mr. Malik blamed the Taliban. He said the Pakistani people had a message of defiance for them.