The air marshal flew back to the United States after the attack and `` felt fine '' the entire 12-hour flight , a U.S. law enforcement official told CNN . `` Out of an abundance of caution , the Centers for Disease Control and Prevention conducted an on-scene screening of the victim when United Flight 143 landed in Houston early Monday morning , '' a statement from the FBI read . ` The air marshal was injected with a syringe containing an `` unknown substance '' the source of which is not known.
The air marshal was injected with a syringe containing an `` unknown substance '' the source of which is not known.