Three accused terrorists, including alleged 9/11 mastermind Khalid Sheikh Mohammed, have reached a plea deal to spare them the death penalty.

According to CNN, the death penalty is no longer an option for Mohammed, Walid Bin ‘Attash, and Mustafa al Hawsawi, prosecutors wrote in a letter that was sent to the families of 9/11 victims and survivors.

"We recognize that the status of the case in general, and this news in particular, will understandably and appropriately elicit intense emotion, and we also realize that the decision to enter into a pre-trial agreement will be met with mixed reactions amongst the thousands of family members who lost loved ones," prosecutors said.

"The decision to enter into a pre-trial agreement after 12 years of pre-trial litigation was not reached lightly; however, it is our collective, reasoned, and good-faith judgment that this resolution is the best path to finality and justice in this case," the letter continued.

The three men have reportedly agreed to plead guilty to all charges relating to the 2001 attacks that killed nearly 3,000 people, marking the worst terrorist attack on US soil in history.

Mohammed and his co-defendants are expected to enter guilty pleas within the next few days.

READ MORE: Celebrities and Politicians React to Donald Trump Rally Shooting, Unite to Condemn Violence

News of the guilty pleas weren't well received by all of the victims' families.

"The prosecution and families have waited 23 years to have our day in court to put on the record what these animals did to our loved ones. They took that opportunity away from us," Jim Smith, husband of the only female police officer who died on Sept. 11, told the New York Post.

"They committed the worst crime in the history of our country, they should receive the highest penalty," he added.

Donald Trump Rally Shooting: Photos From the Scene

See photos from the scene of the shooting at Donald Trump's Pennsylvania campaign rally.

Gallery Credit: Jacklyn Krol

More From PopCrush