Union officials representing prison guards stood outside the Division of Corrections to call for a change in leadership following the assaults on prison guards at a correctional institution in Cumberland. (Amy Davis/Baltimore Sun video)

The inmate's handwritten letter, addressed to a tier captain in the North Branch Correctional Institution in Cumberland, was clear: Remove two specific corrections officers from the housing unit, or they would be violently attacked.

"I will not let you know when your time has run out," wrote the inmate, who claimed to control the marching orders of other prisoners in the maximum-security state prison.

By Monday, several days after the letter was sent, officials had warned one of the officers named in the letter, but not the other — a violation of corrections department policy, officials said.

About 8:40 a.m. Monday, authorities say, the unwarned officer was stabbed multiple times in the neck and head with a homemade weapon, allegedly by an inmate serving a life sentence for murder.

The officer was rushed to an area hospital with what officials say were non-life-threatening injuries.

The Department of Public Safety and Correctional Services is now investigating the incident "to ascertain why the notification of the threat was not made to the officer," department spokesman Rick Binetti said.

"Appropriate disciplinary action will be taken if staff are found to have violated the notification process," Binetti said.

Union officials say that's not enough.

The stabbing, in which two other officers suffered less severe injuries, was the latest in a string of inmate-on-officer attacks at the North Branch facility this summer. Patrick Moran, president of AFSCME Maryland, said 15 officers have been assaulted since the end of June.

Three North Branch inmates have been killed in the past year.

Moran said corrections officials have ordered few changes in response to the violence — and now they must be held accountable.

During a news conference Tuesday, Moran called the failure to warn the officer of the active threat "unconscionable." With other union officials, he called for the immediate resignation of three high-level department officials: J. Michael Stouffer, the deputy secretary of operations; Jon P. Galley, the executive director of northern regional operations; and Rodrick R. Sowers, director of corrections in the northern region.

"They knew there was going to be an assault, they had the intel .... and did nothing," Moran said as several current and retired corrections officers stood behind him outside a corrections department building in Baltimore.

"They need to do the right thing. They need to step aside," Moran said.

Corrections officials did not respond to the calls for resignations. Galley declined to comment, and Stouffer and Sowers could not be reached.

The demands come at a time of increased scrutiny for the corrections department. Officials pledged reforms after federal prosecutors alleged that inmates at the Baltimore City Detention Center associated with the Black Guerrilla Family gang conspired with 13 corrections officers to smuggle in drugs, cellphones and other contraband.

Black Guerrilla Family leader Tavon White, the ringleader of the scheme, pleaded guilty Tuesday to racketeering.

Attention has shifted west as the number of assaults on staff at North Branch has spiked.

According to Jeff Grabenstein, president of AFSCME Local 898 at North Branch and a corrections employee there, the problems plaguing the Baltimore jail and the Cumberland prison are related.

The transfer of some inmates from Baltimore to North Branch after the federal indictment was handed down in April, he said, "brought some trouble along with it."