An Army Reserve unit undergoing demolition training at Utah's Camp Williams last month reported all of its munitions had been used as planned.

Sunday night, the Provo Police Department offered a possible counterpoint.

Acting on a tip, the department's bomb squad evacuated an apartment complex, and a bomb-sniffing dog eventually located "a full-sized block of military issued C4 explosive" inside a locked ammo box allegedly belonging to Spc. Adam Michael Garceau, according to a Provo PD Facebook post.

The 21-year-old, who participated in training March 18-20 at Camp Williams with 744th Engineer Company, was booked into Utah County Jail for possession of an explosive and possession of stolen property.

An Army Reserve investigation is underway, spokesman Maj. Oluwole Osibodu said.

"Considering the current national security climate and public safety concerns, the Army Reserve and our command take this matter very seriously and we will do our best to get a full understanding of this incident," Osibodu said in an email.

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A block of C4 allegedly found in the apartment of an Army Reserve member, weeks after he'd participated in demolition training.

Photo Credit: Provo (Utah) Police Department via Facebook

While the training involved a Reserve unit, the Utah National Guard operates the camp's ammunition supply point for all exercises. The visiting unit signed a March 23 consumption report stating that all materials had been used, Guard spokesman Lt. Col. Steven Fairbourn said via email.

The Guard is "conducting an internal informal investigation" into the incident, Fairbourn said, while awaiting the Reserve investigation's report "to identify potential protocols or practices that could enhance safe and effective training at Camp Williams."

The Deseret News, citing local police, reported Garceau told a friend that he hoped to set the C4 off in the desert.