Twenty people are confirmed dead and 300 of the 550 people in the building remain unaccounted for after a car bomb blew a nine-story hole in the Alfred Murrah Federal Building in downtown Oklahoma City this morning. At least 17 of the dead are infants and children killed in a day care center on the premises. Federal officials believe the explosives were packed in a car parked nearby. They said the bomb was as strong as that used in theWorld Trade Center attacktwo years ago. The FBI established a command post in Oklahoma City, and President Clinton, at a televised news conference, denounced the bombers as "evil cowards" and promised quick justice: "These people are killers and they must be treated like killers."