Brennan began his CIA career as an analyst and spent 25 years with the agency. He was a daily intelligence briefer for President Bill Clinton. In 1996, he was CIA station chief in Riyadh, Saudi Arabia, when the Khobar Towers bombing killed 19 U.S. servicemen. In 1999, he was appointed chief of staff to George Tenet, then-Director of the CIA. Brennan became deputy executive director of the CIA in March 2001. He was director of the newly created Terrorist Threat Integration Center from 2003 to 2004, an office that sifted through and compiled information for President Bush's daily top secret intelligence briefings and employed the services of analysts from a dozen U.S. agencies and entities.