WEST PALM BEACH, Fla. (AP) — The man accused in the apparent assassination attempt of Donald Trump at a golf course in Florida left behind a note detailing his plans to kill the former president and kept in his car a handwritten list of dates and venues where Trump was to appear, the Justice Department said Monday in foreshadowing additional and more serious charges against him.

The new allegations were included in a detention memo filed ahead of a hearing Monday at which federal prosecutors argued that Ryan Wesley Routh should remain locked up as a flight risk and a threat to public safety. U.S. Magistrate Ryon McCabe agreed, saying the “weight of the evidence against the defendant is strong” and ordered him to stay behind bars.

The latest details were meant to bolster the Justice Department’s contention that the 58-year-old suspect had engaged in a premeditated plan to kill Trump, a plot officials say was thwarted by a Secret Service agent who spotted a rifle poking out of shrubbery on the West Palm Beach golf course where Trump was playing and then opened fire in Routh’s direction.

The note describing Routh’s plans was placed in a box that he dropped off months earlier at the home of an unidentified person who did not open it until after last Sunday’s arrest, prosecutors said. The box also contained ammunition, a metal pipe, building materials, tools, phones and various letters. The person who received the box and contacted law enforcement was not identified in the Justice Department’s detention memo.

One note, addressed “Dear World,” appears to have been premised on the idea that the assassination attempt would be unsuccessful.

“This was an assassination attempt on Donald Trump but I failed you. I tried my best and gave it all the gumption I could muster. It is up to you now to finish the job; and I will offer $150,000 to whomever can complete the job,” the note said, according to prosecutors.

The letter offers “substantial evidence of his intent,” Assistant U.S. Attorney Mark Dispoto said in court Monday.

“That’s the message he wanted to send to the world in advance of this incident” he said.

Routh is currently charged with illegally possessing his gun in spite of multiple felony convictions, including two charges of possessing stolen goods in 2002 in North Carolina, and with possessing a firearm with an obliterated serial number.

But Dispoto said prosecutors would pursue additional charges before a grand jury accusing him of having tried to “assassinate a major political candidate.”

Kristy Militello, an assistant federal public defender representing Routh, asked during Monday’s hearing for Routh to be permitted to live with his sister in Greensboro, N.C., as the case moves forward. She argued that prosecutors had failed to show that he was a threat to the community and noted his track record of habitually showing up for court appearance throughout decades of legal troubles,

Besides the note, prosecutors also cited cellphone records indicating that Routh traveled to West Palm Beach from Greensboro in mid-August, and that he was near Trump’s golf club and the former president’s Mar-a-Lago residence “on multiple days and times” between August 18 and the day of the apparent attempted assassination.

He was arrested on September 15 after a Secret Service agent who was scoping the Trump International Golf Club for potential security threats saw a partially obscured man’s face, and the barrel of a semiautomatic rifle, aimed directly at him. The agent fired at Routh, who sped away before being stopped by officials in a neighboring county.

The Secret Service has said Routh did not fire any shots and never had Trump in his line of sight.

The Justice Department also said Monday that authorities who searched his car found six cellphones, including one that showed a Google search of how to travel from Palm Beach County to Mexico.

They also found a list with dates in August, September and October and venues where Trump had appeared or was scheduled to, according to prosecutors. A notebook found in his car was filled with criticism of the Russian and Chinese governments and notes about how to join the war on behalf of Ukraine.

The detention memo also cites a book authored by Routh last year in which he lambasted Trump’s approach to foreign policy, including in Ukraine. In the book, he wrote that Iran was “free to assassinate Trump” for having left the nuclear deal.