US federal agents are investigating the background of a former US Marine for plotting an ISIS-inspired attack in San Francisco on Christmas, court documents revealed. Tow-truck driver Everitt Aaron Jameson, 26, was planning to target the citys busy Pier 39 tourist spot, according to an affidavit submitted Friday by FBI Special Agent Christopher McKinney. He was charged in the Eastern District Court of California with attempting to provide material support to a designated foreign terrorist organization and faces up to 20 years in prison if convicted. A preliminary hearing is slated for January 5. The suspect is said to have outlined to undercover agents a plan to use explosives to target crowds at the pier -- which is lined with restaurants, shops and bars -- between December 18 and 25 because "Christmas was the perfect day to commit the attack." Jameson professed not to need an escape plan as he was "ready to die," the document said. As a former soldier, he said, "I have been trained in combat and things of war." He asked for help obtaining a fully automatic military assault rifle, either an M-16 or an AK-47, along with ammunition and materials to make explosives, including nails, timers and remote detonators, the affidavit said. However, Jameson told the undercover agent Monday that he had reconsidered and felt he could not carry out the attack after all, the affidavit says. He denied the allegations during a hearing in federal court Friday. The FBI said the public was "never in imminent danger." San Francisco Acting Mayor London Breed said there are no other known threats, though police increased their presence throughout the city after being notified of the FBI investigation several days ago. "San Francisco is a city that proudly champions democracy, freedom and liberty. Sadly, that makes our home a target," Breed said in a statement. "We will not allow the thwarted attempts of one dangerous individual to disrupt our way of life. We will remain vigilant and continue to protect our city from any threat." McKinney acknowledged an FBI misstep that could have endangered the investigation. FBI agents raided the suspects home in Modesto, California on Wednesday, allegedly finding his last will and testament along with a .22-caliber Winchester rifle, handguns, fireworks and ammunition. Jameson attended basic training with the Marine Corps in 2009, obtaining a "sharpshooter" rifle qualification, the FBI said, but was discharged after failing to disclose a history of asthma. According to McKinney, Jameson selected Pier 39 because he "knew it was a heavily crowded area." "Jameson explained that he also desired to use explosives" in an attack that could involve his tow truck as an additional weapon, McKinney stated. The suspect revealed his plans to an undercover FBI agent he believed to be a senior leader of ISIS, according to the court document. Jameson said the US needed "another attack like New York or San Bernardino," involving vehicles and firearms. He had voiced support for the October 31 attack in New York in which an extremist drove a pickup truck into a crowded bike path, killing eight. In the 2015 attack in San Bernardino, California, a married couple used firearms to kill 14 people at a government building. According to the 11-page criminal complaint, Jameson "has espoused radical beliefs." He had "liked" pro-ISIS posts on Facebook, including an image of Santa Claus standing in New York with explosives. "The FBI isnt saying much to me, but I know my son wouldnt harm nobody. He wouldnt do that to innocent people," the suspects father, Gordon Jameson said, adding that he had been told his son was on suicide watch. The Sacramento Bee quoted the grandfather of Jamesons ex-wife Ashley Monett Jameson as saying the couple have two young children. The paper said Ashley Jameson is in prison -- the reason was unclear -- and the children are in foster care. Gordon Jameson said his son was "devastated" after being told he would never regain custody of his children.