White House correspondents' suspect Cole Allen will stay in custody, Pirro says he fired shotgun

Cole Allen,the suspect inthe White House Correspondents' Association Dinnershooting, conceded to remain detained pending further legal proceedings in his case, his attorney said at his detention hearing on Thursday.

Allen, dressed in an orange jail jumpsuit, appeared calm and did not speak during the hearing.

Allen, 31, faces three felony counts of attempted assassination of the President of the United States, transportation of a firearm and ammunition over state lines with the intent to commit a felony and discharge of a firearm during a crime of violence. He has not entered a plea and is set to return to court on May 11.

The California native-- who was carrying a shotgun, a pistol and knives -- was tackled by law enforcement after Saturday night'sgunfire inside the Washington, D.C., Hilton hotel, where thousands of journalists as well as President Donald Trump and members of his Cabinet were gathered for the annual dinner. Allen did not reach the ballroom, where the dinner was underway. A Secret Service member was shot during the incident, but the bullet hit the agent's protective vest, officials said.

In an overnight court filing, Allen's attorneys questioned what evidence the government has to determine Allen fired his weapon.

According to U.S. Attorney for D.C. Jeanine Pirro, "We know [Allen] fired off that 12-gauge shotgun one time."

"The cartridge was still in the weapon. He fired that gun in the direction of the Secret Service officer," Pirro told Fox News on Thursday. "The Secret Service officer fired his weapon five times and we know that based on the number of bullets that were left in the weapon."

The Secret Service agent did not shoot himself, she said.

"We're waiting for the official ballistics test, but at the same time we filed papers in court this morning for the detention hearing today indicating that this defendant was calculated, he was premeditated and he had every intention of killing the president and anyone who got in his way," she said.

Pirro said Allen will face additional charges. She also said investigators are searching for anyone he might've threatened by name.

Allen's court appearance came a day after federal prosecutors filed a detention memo, supporting their request for a judge to hold the defendant in custody pending trial.

"The defendant attempted to kill the President of the United States, Donald J. Trump. The crimes with which the defendant is charged are among the most serious in the United States Code, and the evidence of his guilt is overwhelming," prosecutors wrote.

Under what prosecutors titled in court records as "The Defendant's Assassination Plan," prosecutors cited his writings in which he allegedly laid out his plan to target top members of the Trump administration, according to the memo.

The suspect also sent a prescheduled email to his employer minutes before launching the attack, in which he allegedly apologized for his "unprofessionality [sic]," according to a pretrial detention memo prosecutors filed in federal court on Wednesday.

"Consider me to be submitting my resignation effective immediately (if it matters.)," Cole allegedly wrote in the email, according to the memo.

The tutoring company C2 Education, where Allen purportedly worked, said they are cooperating "fully" with law enforcement and denounced the "horrifying incident" at the correspondents' Dinner, but omitted details of Allen's work history.

"We were shocked to hear the news of the horrifying incident that transpired at the White House Correspondents' Dinner," the tutoring company said in a statement on Sunday. "We are cooperating fully with law enforcement to assist them in their investigation. Violence of any kind is never the answer."

ABC News' Luke Barr and Bill Hutchinson contributed to this report.