Gregory Lee Rodvelt, 71, from Oregon, US, was found guilty by a jury on Tuesday of hospitalising an officer after learning the government had appointed a lawyer to sell off his property in Williams, Oregon.
Rodvelt, who was already in jail in an Arizona prison for a separate incident, confessed to the FBI ahead of the raid that "fishing line and a tripwire" were deliberately placed “across the property gate that went to a round hot tub that was on its side set to roll down the hill and hit whoever comes through the gate."
Bomb specialists with the FBI and police went to inspect the home after Rodvelt was arrested in Arizona in April 2017 and charged with unlawful possession of explosives, according to FBI Special Agent Jeffrey Gray.
But when the specialists arrived to the man's former home on September 7, 2018 they saw the front gates were blocked by a minivan which "was rigged with two booby traps", police said.
The traps were disarmed but when they arrived to the front of the door, the FBI and police spotted a hot tub tilted at an angle.
Mr Gray said in a written statement: "Rodvelt stated that he set up fishing line and a tripwire across the property gate that went to a round hot tub that was on its side set to roll down the hill and hit whoever comes through the gate."
"Rodvelt described it by referencing the 'stone rolling down in the Indiana Jones Movie."
"Rodvelt said there other tripwires on the property and a spike strip made of nails and wood which was designed to flatten tires. Rodvelt did not provide additional specifics about the tripwires."
Law enforcement officers entered the house "based upon the presence of the aforementioned booby traps" and officers used "an explosive charge to breach the front door," the affidavit says.
Once they were inside, they stumbled upon a wheelchair when "it triggered a homemade shotgun device that discharged a .410 shotgun shell that struck the FBI bomb technician below the knee," the US attorney's office said.
The agent was rushed to hospital where he was treated for his injuries and later released, according to authorities.
Rodvelt could face up to 20 years in jail when he's sentenced, prosecutors have said.
“Assaulting a federal officer with a deadly or dangerous weapon is punishable by up to 20 years in federal prison. Using and discharging a firearm during and in relation to a crime of violence is punishable by up to life in federal prison,” a police statement revealed.
However, his defence lawyer Benjamin Kim said on Wednesday "that's an unrealistic maximum" sentence.