Kyle Odom, 30, was arrested on suspicion of attempted murder by secret service agents after they saw him toss something over the iron fence at the front of the White House.
It was two days after he allegedly shot Evangelical pastor Tim Remington in the head and back at point blank range in the car park of his church in Coeur d’Alene, Idaho.
Unbelievably, Mr Remington survived the attack and has woken from the coma it left him in.
Police said Odom had earlier sent a rambling 21-page “manifesto” to his parents and media outlets which allegedly claimed he shot the pastor because he was an alien involved in a conspiracy here on Earth, with members of congress, to enslave all humans.
The message said: “My last resort was to take actions to bring this to the public’s attention.
“I hope that something good comes of it. Just realise that I’m a good person, and I’m completely innocent.
“Also realise that the ‘people’ I killed are not what you think.”
The letter linked to Odom, who has a history of mental illness, described his past with the Marine Corps and studying genetics at university.
Pastor Tim Remington (above)
It added: “Check my personal documents.
“As you can see, I’m pretty smart. I’m also 100 per cent sane, zero per cent crazy.”
The papers also described “hypersexual,” mind-controlling Martians.
It says Odum begun experimenting with mediation at university, which led to an out of body experience and a meeting with a “blue being”.
— Hayley Guenthner (@KHQHayley) March 9, 2016
From then on, he soon allegedly became paranoid that he had alien classmates who were trying to convince him to become a school massacre shooter.
The manifesto said this made him return home to Coeur d’Alene.
There, he began attending the Altar Church and came into contact with Pastor Remington, who began texting him.
The paper linked to Odom said: “At first they were innocuous bible messages, but then he started threatening me.
etchings of aliens from Odom’s manifesto
“He sent messages talking about ‘their power’ and other things. He did all of this through bible verses so it would not look suspicious.”
Odom later allegedly started strange sexual experiences, saying: “It felt like someone was manually pumping blood into my penis”
The former student allegedly became convinced he was going to be turned into a sex slave, but these “Martians that looked like giant green frogs with proboscises on the top of their heads.”
The papers said Odum fled his home town again, but aliens threatened to harm his family, so he returned.
It added when he returned to the church, he said he smelt “a reptile and vinegar smell.”
— Jeff Hite (@KHQJeff) March 9, 2016
The papers said: “I realised that whoever I was dealing with was extraterrestrial, so I became very scared.”
It added: “My life was ruined.
“Ruined by an intelligent species of amphibian-humanoid from Mars.”
It was then he allegedly shot the pastor, for being a key part of the alien plan.
Two days later he drove Boise, Idaho, and flew to Washington DC.
The manifesto said of Barack Obama: “I want to thank you for your sacrifice to this country,” and that the president was also controlled by aliens.
The papers listed 50 members of Congress — from both parties, plus 36 high-ranking Israelis, who were described as actually being aliens.
The papers said: “Martians are ubiquitous. They exist at every level of society in every nation. Some have blue collar jobs, while other occupy positions of power.
“They control our government, our military, and Corporate America as well. They keep track of every ‘wild’ human on the planet and manage us like animals in a zoo. Our ‘freedom’ is a carefully crafted illusion.”
The same day Odum arrived in Washington a message appeared on his Facebook page, which has an alien as a profile picture, that said: “Things are not what they appear to be.
“The world is ruled by [an] ancient civilisation from Mars.
“Pastor Tim was one of them, and he was the reason my life was ruined.
“I will be sharing my story with as many people as possible. I don’t have time right now, they are chasing me.
“I shot Pastor Tim 12 times.
“There is no way any human could have survived that event.”
Odum remains in custody.