The man who authorities say sat with a rifle in the trees where Donald Trump was golfing earlier this month in West Palm Beach, Florida, previously wrote a letter stating “this was an assassination attempt on Donald Trump,” according to a new filing Monday by federal prosecutors. Shortly after the filing, a federal magistrate judge ordered Ryan Wesley Routh to remain detained pending further proceedings. A witness told investigators that Routh had dropped off a box at his home months before, which “contained ammunition, a metal pipe, miscellaneous building materials, tools, four phones, and various letters.” After learning of the apparent assassination attempt, the witness opened the box, according to the filing. One letter, addressed to “The World” said: “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.” Trump “ended relations with Iran like a child and now the Middle East has unraveled,” the letter says. Routh, 58, was charged with two firearm offenses last week after allegedly fleeing the Trump International Golf Course. More serious charges could be brought in the case as the investigation continues. “I find that the weight of the evidence against the defendant is strong,” Judge Ryon McCabe said at the end of the nearly three hour hearing Monday. The judge cited the letter Routh allegedly wrote about the assassination attempt as well as other evidence prosecutors presented, including that agents found a fingerprint belonging to Routh on tape used to attach a scope to the rifle found outside the golf course. Prosecutors say a Secret Service agent fired at Routh after spotting a rifle poking out of the tree line several holes ahead of where Trump was golfing on September 15, and that Routh was spotted by a witness running away from the scene and driving off. The complaint against Routh says cell phone data shows he may have been lying in wait for nearly 12 hours at the golf course. He was arrested after law enforcement spotted his car driving on a nearby highway. Prosecutors say Routh was in the area of Trump’s golf course and the former president’s Mar-a-Lago residence across multiple days in the month before he was arrested and had a Google search of how to travel from Florida to Mexico in one of his phones. Routh also had a handwritten list of dates and venues where Trump has or was expected to appear in the lead-up to the 2024 presidential election. Prosecutors wrote that Routh had traveled to West Palm Beach from North Carolina on August 14. Cell phone data shows him near Trump’s Mar-a-Lago residence and the golf course “multiple days and times” between August 18 and September 15, the day he was arrested, prosecutors say. While searching Routh’s car, agents found six cell phones, one of which included “a Google search of how to travel from Palm Beach County to Mexico.” “The agents also found 12 pairs of gloves; a Hawaii Driver’s License in the Defendant’s name; a passport in the Defendant’s name,” the filing says. Routh’s recent background included a stint in Ukraine, where he unsuccessfully tried to be recruited to fight Russia, as well as time in Hawaii working in construction. In online posts, frequently focused on US politics and global events, Routh said he voted for Trump in 2016 but that the president had become a disappointment, adding that “I will be glad when you gone.” Routh, in a self-published book, also told the country of Iran: “You are free to assassinate Trump.” Routh’s position “was directly in line with” the very next hole from where Trump was golfing, the court filing states. While Trump was on the 5th hole, a Secret Service agent was clearing the area of the 6th hole, riding a golf cart along the fence, which drew a boundary between the course and a major road on the other side. When clearing the area, “the Agent spotted the partially obscured face of a man in the brush along the fence line,” prosecutors wrote. The man’s position “was directly in line with the 6th hole green,” according to the filing. After spotting the man and realizing his rifle was pointed at the agent, prosecutors say “the Agent jumped out of the golf cart, drew his weapon, and began backing away.” Then, when the Secret Service agent saw the barrel of the rifle move, the agent fired at the man and then moved behind a tree to reload his gun, according to the filing. When the agent looked back, the man, later identified by authorities as Routh, was gone. “The Agent called out over his radio that shots had been fired by the Agent and that there was a subject with a rifle,” prosecutors said. Prosecutors say Routh’s rifle had a scope attached, as well as an extended magazine, allowing the gun to hold more ammunition. The rifle was loaded with 11 bullets with one in the chamber, ready to fire, according to the court filing. This story has been updated with additional developments.