Houston ? The gunman in an apparent murder-suicide at the Johnson Space Center targeted a NASA worker he feared could get him fired, police said Saturday.

William Phillips had received a poor job review a month before authorities said he smuggled a revolver into the space center, shot David Beverly and barricaded himself with a hostage before killing himself in a building that houses communications and tracking systems for the space shuttle. The hostage escaped.

Police Chief Harold Hurtt said Phillips bought the .38-caliber revolver March 18, two days after receiving an e-mail citing deficiencies in his job performance.

A copy of the e-mail was found in Phillips’ lunch bag on the day of the shootings, police Lt. Larry Baimbridge said.

Space agency spokesman John Ira Petty said Saturday that NASA was conducting what he called a continuous review of security procedures. Petty would not discuss specifics, saying the apparent murder-suicide was a police matter.

To enter the space center, workers must show an ID badge as they drive past a security guard. The badge allows workers access to designated buildings.