A manifesto understood to have been sent to family by the suspect involved in the Washington, D.C., shooting at the White House Correspondents' Association has provided law enforcement with crucial information about his gun and bullet choices.

Suspected gunman Cole Allen reportedly sent a chilling anti-President Trump manifesto to his family shortly before opening fire at Saturday night's White House Correspondents' Dinner, naming himself the "Friendly Federal Assassin." He indicated that he was hell-bent on killing Trump administration officials, The Washington Post reported.

In the manifesto, Allen allegedly said he planned to use buckshot instead of slugs "In order to minimize casualties. He is said to have added, "I will also be using buckshot rather than slugs (less penetration through walls)," before confirming that he would be willing to kill everyone present, writes the NYP.

A US official said the unhinged note, sent about 10 minutes before the shooting, laid out his "targets" as including "Administration officials (not including [FBI Director Kash] Patel)... prioritized from highest-ranking to lowest."

"I am no longer willing to permit a peadophile, rapist, and traitor to coat my hands with his crimes," Allen apparently wrote in the manifesto, referring to allegations critics have made against Trump and which have been denied by the President.

"I would still go through most everyone here to get to the targets if it were absolutely necessary (on the basis that most people chose to attend a speech by a pedophile, rapist, and traitor, and are thus complicit) but I really hope it doesn't come to that," Allen apparently added.

Within the document, Allen allegedly called upon his Christian faith, presenting sections of it as "rebuttals" to expected criticism of his intended actions. He also touched upon contentious political issues, including the Trump administration's strikes on Venezuelan drug boats and the detention of illegal migrants.

"Turning the other cheek is for when you yourself are oppressed. I'm not the person raped in a detention camp. I'm not the fisherman executed without trial," Allen is understood to have written in the deeply disturbing document, which a family member handed over to police, according to the US official.

"I'm not a schoolkid blown up, or a child starved, or a teenage girl abused by the many criminals in this administration. Turning the other cheek when someone else is oppressed is not Christian behavior; it is complicity in the oppressor's crimes," the manifesto continued, according to the New York Post.

An official informed The Post that Allen's brother reached out to the New London, Conn., police department regarding the manifesto. The Secret Service has interviewed Allen's sister in Rockville, Md., and discovered that he regularly made politically extreme comments and spoke of doing "something" to tackle the world's problems. These documents are currently under review as part of the active investigation, according to law enforcement and White House officials who spoke with CBS News.

Sources told the outlet that the writings indicated the suspect had intended to target administration officials, though they contained no direct mention of the White House Correspondents' Association dinner. Investigators also discovered anti-Trump and anti-Christian material on the suspect's social media accounts.

The individual accused of attempting to force his way into the ballroom during the White House Correspondents' Association dinner while carrying firearms and knives had travelled across the country prior to the event state officials, and is believed to have been plotting to target President Donald Trump and other senior administration figures, acting Attorney General Todd Blanche revealed on Sunday.

Blanche revealed that investigators believe the suspect travelled by train from California to Chicago before making his way to Washington, where he checked into the hotel hosting Saturday night's high-profile dinner several days beforehand. Authorities stated he attempted to force his way into the vast Washington Hilton ballroom but was overpowered during a frantic altercation that resulted in shots being fired, President Donald Trump being hastily escorted from the stage, and guests diving beneath tables for safety.

"It does appear that he did in fact set out to target folks who work in the administration, likely including the president," Blanche told NBC's "Meet the Press."

Blanche noted that investigators believe the suspect acquired the two firearms found on his person within the past couple of years. He has refused to cooperate with authorities and is expected to face a raft of charges on Monday.

Footage shared by Trump appears to show the suspect darting past security barriers as Secret Service agents closed in on him. Authorities confirmed that one officer was struck on a bullet-resistant vest and is recovering. Police stated the suspect was detained without injury but was taken to a medical facility for evaluation.

"He failed," Blanche said on CBS's Face the Nation."Law enforcement did their jobs." Investigators believe the suspect fired the shot that struck the Secret Service officer, who is expected to make a full recovery, Blanche confirmed. "He's going to be great, he's going to be fine, and thank God he was wearing a bulletproof vest," Blanche said on Sunday on ABC's "This Week."

Online profiles apparently belonging to the suspect suggest he is a well-educated tutor and amateur video game developer.