Story highlights Richard Sandberg, 35, is arrested in a Denver suburb by federal authorities

In an affidavit, authorities say Sandberg built deadly explosive devices

He also had military-grade grenades he wanted to sell or trade for cocaine

A Colorado man who lived near a park crafted explosives he claimed could kill everyone within 20 meters, hoping to trade the bombs and other weapons for cocaine or cash, authorities said.

Special agents with the federal Bureau of Alcohol, Tobacco, Firearms and Explosives arrested Richard Sandberg, 35, on Thursday morning as he was heading to work, said Jeffrey Dorschner, a spokesman for the U.S. Attorney's Office in Colorado

In the afternoon, he appeared in federal court, where he was ordered held without bond until at least a detention hearing Tuesday.

His arrest followed an undercover sting that revealed the suspect had an arsenal of "homemade" improvised explosive devices and military-grade grenades in his suburban Denver home, according to an affidavit filed by an ATF agent in federal court.

The investigation began a week ago, when a Denver police detective alerted an ATF agent about a claim from a "reliable" informant.

The informant had gone to Sandberg's house and saw "numerous hand firearms and hand grenades" the suspect "wanted to trade ... for cocaine," according to the affidavit.

That night, an undercover ATF agent talked over the phone with Sandberg, who said he was a former member of a Marine special operations unit.

He claimed to have 18 M67 grenades -- which are available only in the military -- that he said he'd sell for $300 each, the ATF agent wrote.

According to the affidavit, Sandberg said he'd built some explosive devices with items available at hardware stores. He said you'd need a "formula" to know how to make them blow up -- and they had a "kill zone" of 20 meters and a "hurt zone" of 60 meters.

The devices, he said, are "not firecrackers, not things to play with: (They are) life or death."

The undercover agent told Sandberg he was going out of town to pick up illicit drugs, then met up with him Tuesday evening at the suspect's house in Jefferson County, about 15 miles southwest of the Colorado capital.

Once there, Sandberg detailed his military background as a demolition expert who'd served in Iraq, Somalia and Pakistan, and had been trained "to build bombs and kill people," the affidavit states.

He expressed contempt for President Barack Obama and his administration, and the ATF in particular.

He later showed the undercover agent "an iron-plated door barricade with gun turret/cutouts." He said he was prepared to use it if law enforcement agents moved in on his house -- adding he had several thousand rounds of ammunition.

"Sandberg made numerous threatening statements toward law enforcement (that if they) came inside his house to take his guns, it would be a bad day for them and lots of them would die," the affidavit reads. "Sandberg stated that he was ready and willing to die."

The suspect then showed off about six pipe bombs and 22 silver "crickets" (small explosive devices) and claimed that he "could manufacture anything (the agent) wanted, including having access to C4 plastic explosives and blasting caps."

The undercover agent left with two pipe bombs and a cricket, with Sandberg saying if he "liked them they could set up a trade for cocaine." Authorities later tested them, and determined they qualified as "destructive devices" under federal law.

Sandberg's arrest came two days later.

Despite his promise of bloodshed, he was taken into custody -- away from the firepower he kept at home -- without incident. He is charged with one count of possession of a firearm, though more charges could be forthcoming.

Swarms of law enforcement agents, including three bomb squads, descended on Sandberg's residence -- which sported a Marine flag in the yard and a "Fire Obama" sign in a window. His home is in the Friendly Hills neighborhood, which features recently built two-story houses.

They found a number of devices as well as grenades, which can only be obtained through the military. The devices were removed from the site and rendered safe, according to Dorschner.

As children rolled by in wagons, Tom Cole told CNN affiliate KUSA about how he had heard him doing metalwork into the night.

"There were many times this goes on until 9 o'clock at night, and you hear a grinder," Cole said.

Another neighbor, Michelle Chalupa, told CNN affiliate KMGH her children had "talked to (Sandberg) before (and) he seemed like a very nice guy."

"It's so scary," she said. "... I'm thankful that whatever operation found it before somebody was hurt."