Alleged Trump golf course gunman wrote "This was an assassination attempt" in letter

• Prosecutors have argued Routh poses too much of a risk and should remain in custody.
• Routh was charged with possession of a firearm by a convicted felon and possession of a firearm with an obliterated serial number in his initial appearance.

Driving the news: In a court filing Monday, the Justice Department shared a letter Routh allegedly wrote months before the September incident saying, "This was an assassination attempt on Donald Trump but I failed you."

• The handwritten letter, addressed "Dear World," continued, according to prosectors: "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."

Zoom out: Prosecutors allege they were contacted by a witness Wednesday who told them Routh had dropped off a box that contained the letter at his residence several months prior.

• The box also held ammunition, a metal pipe, miscellaneous building materials, tools, four phones and other letters, court filings allege.
• The unnamed witness did not open the box until after Routh's arrest, per court filings.

Flashback: Routh has an extensive criminal record, including being convicted of two felonies in North Carolina in December 2002 and March 2010.

Go deeper: Read: Criminal complaint filed against the Trump assassination attempt suspect