A gunman has killed a male hostage and himself during a stand-off at Nasa's Johnson Space Center in Houston, Texas.Police, who had surrounded the scene and entered when they heard a gunshot, also found a second hostage, a woman, who was alive but tied up with tape.Police Capt Dwayne Ready said officers were called to the scene at about 1340 (1840 GMT) after a man was seen with a gun and two shots were heard.Nasa named the gunman as Bill Phillips, a contract engineer at the site.The hostages were named as David Beverly and Fran Crenshaw, though the names were not confirmed by police.
