Two death row inmates who previously killed a correctional officer and another inmate fired shots from makeshift guns at staff at the State Penitentiary at Parchman according to authorities.
No one was injured during the incidents at Unit 32-C, said Corrections Commissioner Robert Johnson. 
Inmate Willie Russell, who three years ago came within minutes of being executed, is accused of firing a shot through a food tray slot in the door of his cell on the morning of December 6, when an officer walked past, Johnson said.
In an adjacent cell, inmate Jimmy Mack, who last year stabbed to death another death row inmate, apparently discharged a similar device when officers went into his cell, Johnson said.
Johnson said officers investigating the incident with Russell became suspicious of Mack.
'When the entry team went in, it sounded like a discharge in Mack's cell,' Johnson said. 
Johnson said the 'zip' guns, hollow metal tubes in which a bullet is inserted, may have been made from a radio antenna. They fire by striking the primer on the cartridge with a nail.
Johnson said it wasn't an escape attempt.
'It was an attempt to harm staff members. Certainly you are not going to be able to escape from maximum security with a zip gun,' he said.
Russell, 40, was sentenced to die for the July 18, 1989, stabbing death of correctional officer Argentra Cotton at Unit 24-B. Russell had previously been convicted of robbery, kidnapping and escape. He abducted a officer at the University of Mississippi Medical Center in Jackson when he was there for medical treatment in March 1987 and led police on a high-speed chase into rural Hinds County.
Russell came within less than an hour of execution on Jan. 21, 1997, before the 5th U.S. Circuit Court of Appeals issued a stay.
Mack, 31, is awaiting execution for the 1990 beating death of Henry Fulton of Gunnison during a burglary. 
Mack used a homemade knife or 'shank' to stab fellow death row inmate Donald Leroy Evans to death on Jan. 4, 1999. Mack pleaded guilty to manslaughter and was sentenced to 20 years.
Other inmates recently told The Clarion-Ledger in interviews and letters they believed prisoners were waiting for an opportunity to try to kill an officer or another inmate. Woolard said he thought the motive would be to get to death row because inmates there enjoy radios, television and other privileges denied to the other maximum-security prisoners.