Carroll County Sheriff Dale Williams said it happened Monday afternoon at a gas drilling rig near Carrolton, southeast of Canton.
The injured man, 21-year-old Alex Cox, told the sheriff that he and the other victim were using drilling equipment and hadn't hooked up a safety line designed to keep it from swinging around and striking workers.
The dead man's name hasn't been released.
Cox fell backward and suffered a severe laceration to the back of his head.
Media reports said the rig is owned by R.E. Gas Development, a subsidiary of Rex Energy Corp.
The investigation is continuing.