Sheriff Billy Sollie also said the FBI had seized a home computer belonging to the killer, Doug Williams.
Nine people were injured in the shooting rampage, and some were still hospitalized today.
Co-workers said the 48-year-old Williams had had run-ins with management and several fellow employees.
Some of the 138 employees at the plant said Williams, who was white, was a racist. Eight of the 14 shooting victims were black, including four of the five who were killed.
Authorities are still interviewing the plant's employees Wednesday.
Brenda Dubose, a Lockheed employee recovering at home from shotgun wounds to the face and hand, said she noticed immediately when Williams entered the ethics meeting.
She says he was carrying several guns and Williams shouted an obscene remark before the shooting rampage.
Dubose said the remark could have been directed at plant manager Steve Cobb, who was wounded, or at Sam Cockrell, a black man who had had an earlier dispute with Williams and who died in the attack.
Sollie said all the shooting victims were hit by shotgun blasts.