The man who shot dead a fellow Nasa worker before turning the gun on himself was undergoing a job review for poor performance and feared being sacked.

The man who shot and killed another NASA worker before turning the gun on himself was undergoing a job review for poor performance and feared being fired, officials said tonight.

Nasa is concentrating on a review of its security procedures as officials try to figure out today how a contract worker smuggled a handgun into the Johnson Space Centre, where he killed another employee and himself.