When police entered the home of Ryan L. McManigal Friday after an hourslong standoff, they were expecting to find firearms.

The peroxide-based explosives stored in 5 gallon buckets throughout the residence, however, was a surprise.

“We did not expect a pretty massive explosive device,” said South Jordan Police Lt. Matt Pennington. “Some of the stuff I heard the agents and bomb techs throwing around was that this is the most they had ever seen in person.”

On Monday, South Jordan police, with the assistance of FBI bomb technicians and the FBI lab, determined the explosives were peroxide-based. Police in a press release said the explosives were manufactured by McManigal, 42, in his home.

Read more: KSL