A Californian man, allegedly arming himself against a feared Bill Gates 5G coronavirus vaccine conspiracy to track Americans, was placed in psychiatric hold for three days while police seized unregistered shotguns from his home.

The San Diego City Attorney's Office said they obtained a Gun Violence Restraining Order against the 52-year-old after he told family and friends about his plan to arm himself during the Covid-19 pandemic, which he claimed was an elaborate hoax to scare Americans into vaccines that made people trackable through 5G towers.

Police were called after the man allegedly became "enraged" when denied the purchase of ammunition in what he believed was a government plan targeting him, saying "I guess I'm going to have to take things into my own hands".

Officials said the purchase was denied due to a prior conviction. The man is on probation for a drink-driving conviction and is prohibited from owning firearms until 2025.

When confronted at his Rancho Peñasquitos home, the man allegedly appeared to exhibit psychotic and delusional behaviour and was determined to be a danger to others, stating he needed to arm himself against the Microsoft founder and the government.

Gates has been the focus of alternate hypothesis over the cause and purpose of the coronavirus pandemic due to the work the Bill and Melinda Gates Foundation has done with experiential vaccines.

In response to questions, the respondent was said to be aggressive and confrontational, ranting and fidgeting. At one point he allegedly said, "people are going to try and get me and I need to defend myself".

Police seized three shotguns while the man was apprehended for evaluation and placed on a 72-hour psychiatric hold.

"Stress from the Covid-19 public health crisis is exacerbating anxiety and mental health struggles for many," City Attorney Mara W Elliott said.

"Thanks to public vigilance, police were able to safely intervene and remove firearms from someone who presented a danger to himself and others before he resorted to violence."