(CNN) A former US Marine talked with an undercover FBI employee about carrying out a terror attack over the holidays at Pier 39, a busy shopping and tourist area in San Francisco, according to an affidavit filed in US District Court in California on Friday.

Everitt Aaron Jameson, 26, of Modesto, California, was arrested and charged with attempting to provide material support to a foreign terrorist organization, the Justice Department said in a news release

Though there are no additional known threats to the city, San Francisco police will be increasing their presence in light of the alleged terror plot, acting Mayor London Breed said in a statement. The spokesperson for the local FBI office said there are no known credible threats in the Bay Area.

CNN has not been able to contact Jameson's lawyer for comment.

The FBI started watching Jameson in September after becoming aware of social media activity in which he "liked" or "loved" posts about terror attacks and ISIS, the affidavit said. Undercover employees of the FBI posed as supporters of ISIS and contacted Jameson, the affidavit said.

Everitt Aaron Jameson

Jameson met with an undercover employee on December 16 and told them he wanted to conduct a terror attack using weapons and explosives at Pier 39, the affidavit said.

Jameson, saying he was familiar with the layout of the site, wanted to use explosives to "funnel" people into a location where he could inflict casualties, the affidavit said. "Jameson also stated that Christmas was the perfect day to commit the attack," the affidavit said.

The attack would be styled after the October 31 attack in New York City in which a man drove a truck down a bike lane, killing eight people, the affidavit said.

Jameson said he'd just started working as a tow truck driver, which could help in the attack, the affidavit said. He expressed loyalty to ISIS and its leader, Abu Bakr al-Baghdadi, and offered to donate money and contribute his firearms skills, the affidavit said.

Jameson had served in the US Marines in 2009 and attained a sharpshooter rifle qualification. He was later discharged for fraudulent enlistment because he failed to disclose a latent asthma history, the affidavit said.

He asked the undercover agents to provide an assault rifle and explosives and sent them photos of what appeared to be Pier 39, the affidavit said. Jameson told the agent that he would be willing to write "a statement to the brothers," the affidavit by an FBI agent said.

Everitt Aaron Jameson

After several communications on December 18, Jameson appeared to back out, telling an undercover agent, "I also don't think I can do this after all. I've reconsidered," the affidavit said.

On December 20, authorities searched his home in Modesto and found firearms, empty magazines, ammunition and fireworks, the complaint said.

They found a will and a handwritten letter that said "you've allowed Donald Trump to give Al Quds away to the Jews," apparently a reference to the President's decision to recognize Jerusalem as the capital of Israel. The letter writer, identified as Abdallah Abu Everitt Ibn Gordon Al-Amriki, goes on to say, "We have penetrated and infiltrated your disgusting country."

During the search, Jameson talked about supporting ISIS and terrorism and said he would be happy if the attack were carried out.

Jameson remains in custody. He appeared in court on Friday for a first appearance and is scheduled for a detention hearing December 28 and a preliminary hearing January 5.

If convicted, Jameson could be sentenced to 20 years in prison and fined $250,000, the Justice Department said.