Ryan Wesley Routh, 58, allegedly dropped a box off at an unnamed person’s house months before the Sept. 15 assassination attempt. The box “contained ammunition, a metal pipe, miscellaneous building materials, tools, four phones, and various letters,” according to the Justice Department.

The witness did not open the box until learning of the assassination attempt.

In the letter, Routh wrote: “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.”

Routh faces two firearm offense charges, but he will likely face more serious charges as the investigation continues.

Cellphone data reportedly show Routh was staked out in the bushes with a gun for 12 hours before the U.S. Secret Service spotted his rifle muzzle. An agent shot at Routh, prompting him to run away and get into his vehicle. He was quickly arrested on the highway by law enforcement officers, who were able to spot his vehicle.