India, April 27 -- About ten minutes before Saturday's attack, Cole Tomas Allen, the accused shooter at the White House Correspondents' Dinner, texted a lengthy, deranged manifesto to his relatives, The New York Post first reported.

Cole 'coldForce' 'Friendly Federal Assassin' Allen" signed the 1,052-word letter, according to the outlet. It detailed his "rules of engagement" for the shooting and declared that he felt it was his moral obligation to target administration officials.

The document begins with a series of apologies addressed to family members, colleagues, and bystanders of the White House Correspondents' Dinner (WHCD). It then shifts into a political justification, stating dissatisfaction with U.S. leadership and expressing a...