Agents found the explosives while searching the family home of 36-year-old Brad Spafford after being tipped off by a neighbour that he was stockpiling weapons and homemade ammunition.

A court document filed on Monday said Spafford, who works at a machine shop, had used pictures of President Joe Biden for shooting target practice and expressed support for political assassinations.

Some explosives assessed as pipe bombs were found in a backpack in a bedroom on the property, which Spafford shares with his wife and two young children, the document said.

It added that Spafford’s freezer contained a jar of HMTD – a “highly unstable” explosive device – stored alongside food and labelled “Do Not Touch.”

His home also had a notebook of “recipes” for making explosives including grenades, according to the filing.

A neighbour told FBI agents that Spafford had discussed fortifying his property with “a 360-degree turret for a 50-calibre firearm on the roof”.

Prosecutors said Spafford, who has been charged with unlawful possession of a rifle, would likely face additional charges over the explosives, which each carry a maximum sentence of 10 years of imprisonment.

In a separate filing on Tuesday, Spafford’s attorneys defended him as “a hard-working family man with no criminal record” while arguing for him to be released from custody.