(NewsNation) — The man charged in an apparent assassination plan against former President Donald Trump pleaded not guilty to all jury charges against him on Monday.

Ryan Routh’s case will now go to trial.

Prosecutors say Routh admitted to the scheme in a letter that he dropped off at the house of an unnamed witness several months before the alleged assassination attempt. That witness didn’t open the box until after Routh’s arrest.

The box also contained ammunition, a metal pipe, “miscellaneous building materials,” tools, four phones and various letters, according to court documents.

Routh’s lawyers unsuccessfully argued for his release on a $250,000 bond earlier this month. One of Routh’s attorneys, Kristy Militello, said the letter indicated “an intent to fail” at the assassination.

Prosecutors, however, said investigators found a handwritten list of planned Trump appearances in August, September and October.

What is Ryan Routh charged with?  

Routh is charged with possession of a firearm by a convicted felon; possession of a firearm with an obliterated serial number; possession of a firearm in furtherance of a crime of violence; assaulting a federal officer and attempted assassination of a major presidential candidate.

Investigators say Routh pointed a rifle through a tree line on Sept. 15 at Trump’s West Palm Beach, Florida, golf course where the former president and GOP presidential nominee was playing.

Unlike the gunman behind the July 13 assassination attempt in Butler, Pennsylvania, Routh isn’t accused of firing a weapon.

What is Ryan Routh accused of?

Routh was about 400-500 yards (approximately four times the length of an NFL field) away from the former president, crouched in bushes near the golf club perimeter and armed with a weapon that had a scope, according to investigators. Trump was not within his line of sight.

The situation began about 1:30 p.m. local time when authorities received a call reporting shots fired at the golf course where Trump was playing. Those shots came from a U.S. Secret Service agent who spotted a rifle sticking through the fence.

A witness told police the suspect fled the scene in a black Nissan, which police located and stopped about 45 miles north of the golf course.

Martin County Sheriff William D. Snyder told WPTV the man “was not armed when we took him out of the car.”

The FBI, State Department and other U.S. government agencies received tips about Routh at least four times in the years before the apparent attempt, The Associated Press reported.