BAYPORT, Minn. (AP) — An inmate used a weapon to kill an officer at a Minnesota state prison, in the first death on record of an on-duty prison guard in the state, corrections officials said.

State Corrections Commissioner Tom Roy declined to describe the weapon used to kill Officer Joseph Gomm on Wednesday at the state’s flagship prison in Stillwater. Gomm was killed in Stillwater’s industry building, which houses a welding shop and carpentry programs, Roy said at a news conference Wednesday.

The inmate, 42-year-old Edward Muhammad Johnson, is serving a nearly 29-year sentence for the 2002 fatal stabbing of his roommate, Brooke Thompson. Before pleading guilty to second-degree murder in Thompson’s death in 2003, Johnson punched a Hennepin County jail deputy in the eye, the Star Tribune reported .

Officials have said Johnson acted alone in the attack on Gomm, which is under investigation. Gomm, like most guards, was armed only with pepper spray and a radio, Roy said. Guns are typically only used by officers stationed in watch towers and assigned to crisis response teams.

About 1,600 inmates are housed at the 104-year-old Stillwater prison, and about a third of them are serving time for homicide.

The guard’s on-duty killing “is the first in the state, as far as we can verify through our records,” according to Department of Corrections spokeswoman Sarah Fitzgerald.

“The corrections family is reeling from this incident,” Roy said. “We are not accustomed to losing staff.”

Assaults on staff at the state’s prisons are common. According to data from the Department of Corrections, there were 63 such assaults at Minnesota’s adult state prisons during the 2016 fiscal year.

More recent figures weren’t immediately available, but there have been concerns about worsening conditions. At least two attacks on officers at the Oak Park Heights maximum security facility have been made public this year. Just last month, a corrections officer suffered injuries that were not life-threatening in an attack that led to a lockdown. In April, 10 employees were injured in two separate fights in one weekend.

AFSCME Council 5, a union that represents Minnesota state correctional officers, said in a statement it has lobbied state lawmakers for increased staffing and funding to alleviate shortages at correctional facilities, “only to have them voted down by politicians who do not support the safety and security of our Correctional Staff.”

Rogers police Chief Jeff Beahen, president of the Minnesota Law Enforcement Memorial Association, said correctional officers deserve credit for choosing to work among sometimes violent populations with inherent risks while equipped with few tools to protect themselves.

Beahen said Gomm is survived by a sibling and a parent. He said his organization has met with the family and offered a “line-of-duty” funeral.

“He paid the ultimate sacrifice doing what he was sworn to do,” Beahen said.