OKLAHOMA . . . THE THIRD MAN?

Federal marshals this afternoon arrested an Arizona man they believe was traveling with Oklahoma City bombing suspect Timothy McVeigh immediately after theApr. 19 blast. Steven Garrett Colbern was arrested in rural Oatman, Ariz., on an unrelated federal firearms charge; a hotel owner had recognized him as a guest after agents showed his picture around town. The dark-haired Colbern, 35, was described in a news release from Upland, Calif., police as "Steven Garrett Colbern, AKA John Doe No. 2," but FBI officials today refused to say whether he could be the elusive suspect. Officials believe that Colbern might have driven a brown pickup truck spotted by an Oklahoma City police car video camera after the bombing. In the videotape, the truck appeared to be driving in tandem with McVeigh's car, pulled over with McVeigh, waited briefly and then drove off. The truck reportedly carried a bag ofammonium nitrate fertilizerin its bed; police today discovered traces of that substance in a brown truck registered in Colbern's name. Colbern's father, an Oxnard, Calif., dentist, said his son holds a chemistry degree from UCLA.