Ryan W. Routh, the 58-year-old man arrested for attempting to assassinate former American President Donald Trump, had his plan written in a note in which he offered $150,000 to anyone able to kill the former American president.

In a federal court filing on Monday, Mr Routh, in the note, admitted that his attempt on Mr Trump’s life could fail but offered N150,000 to whoever could assassinate Mr Trump.

“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,” Mr Routh wrote in a note found in a box at a friend’s house after his arrest during investigations.

He added, “It is up to you to finish the job; and I will offer $150,000 to whomever can complete the job.”

According to prosecutors, Routh had been surveilling Trump’s golf course in West Palm Beach, Florida, for a month before the incident.

On September 15, he positioned himself near the sixth hole, aiming to shoot Trump with a semiautomatic rifle before a Secret Service agent patrolling a hole ahead spotted Routh and his firearm and foiled his plans.

Mr Routh’s rifle, which had a bullet chambered and contained a total of 11 rounds, was left at the scene, alongside his fingerprint.