A group of 72 retired US generals, admirals, and other high-ranking military officers are pressing the US government to cancel plans to livestream an execution by firing squad.
"We ask the President, our Congressional representatives, and our fellow citizens to act to prevent this barbaric abuse of authority," they wrote in a letter where they also argued the livestream would turn the mass killer into a "martyr".
Last week, the Pentagon announced it would publicly show the 3 December execution of Nidal Hasan, an Army psychiatrist who shot dead 13 unarmed US soldiers at the Fort Hood military base.
Lawmakers from both parties, as well as religious leaders, have criticised the plan.
Last week President Donald Trump said he "absolutely" approved of the livestream plan, but some administration officials are now leaning against it, according to CBS News, the BBC's US media partner. CBS reported thatTrump had not yet made a final decision on the livestream as of Tuesday.
In the open letter released on Wednesday, the former military leaders - which included 45 generals, 12 admirals and several former judge advocates general - said they did not oppose the death penalty being carried out.
But they argued a public execution would violate the US Constitution's protections against cruel and unusual punishment and turn what should be a "solemn and grave punishment" into "a carnival for the enjoyment of voyeurs and spectators".
"This type of exploitative broadcasting - that debases human dignity- will taint the honor of the military that employs it, and a nation that allows it," they also wrote.
"It will be used by our nation's enemies to stoke hatred, harm American soldiers and citizens in the future, and will ensure that Hasan becomes a martyr for attacking and killing his fellow soldiers."
The letter's signatories came from throughout the military and included a handful of officers who retired during Trump's first term. Some also had served during the Iraq and Afghanistan wars.
Hasan said in court that he carried out the shooting at Fort Hood, the deadliest ever non-combat attack on an American base, believing he was protecting Muslims and the Taliban in Afghanistan from the US military. Hasan was shot during the attack and now uses a wheelchair.
Retired Maj Gen Tony Taguba, who led the Army's investigation into reported prisoner abuses at Abu Ghraib in Iraq, and retired Air Force Coll Moe Davis, a prosecutor at the Guatanamo Bay detention centre who called waterboarding torture, signed the letter.
So did Charles Bolden, a US Marine Corps Major General who became the head of Nasa, and a retired Lt Gen Claudia Kennedy, the first woman to become a three-star general in the Army.