Law enforcement officials in Lehigh County Thursday announced the arrests of a father-and-son duo on charges relating to the Election Day incident when an explosive was thrown from a moving vehicle at a Catasauqua church being used as a polling site.

Lehigh County District Attorney Gavin P. Holihan, Capt. Seth J. Kelly, Pennsylvania State Police Troop M Commanding Officer and Catasauqua Borough Police Chief John Wiseman announced charges against Jack Pletz, 24, and Matthew D. Pletz, 56, both of Catasauqua.

Matthew Pletz was arrested on Tuesday night and is in Lehigh County Jail, Allentown, on $50,000 bail. His preliminary hearing is scheduled for 10:45 a.m. May 26 before Magisterial District Judge Michael D’Amore.

Police said Jack Pletz surrendered to police and was scheduled to be arraigned.

They are charged with felony counts of conspiracy to commit weapons of mass destruction – unlawful possession or manufacture, and conspiracy to commit risking a catastrophe, as well as misdemeanor charges of conspiracy to carrying explosives on conveyances, conspiracy to make offensive weapons and conspiracy to possession of prohibited offensive weapons.

State police reported they were called to the area of the Salem United Church of Christ, near the intersection of Walnut and Third streets, for reports of an explosive device that had been detonated. They said first responders found remnants of an explosive device at the intersection and the device was determined to be a red tubular cardboard fragment with melted red end caps and was consistent with a “M-type” explosive device.

Investigators found video surveillance from a nearby location that showed a green 1998 Chevrolet pickup truck traveling north on Third Street toward the intersection of Walnut Street. The driver was identified as Jack Pletz.

Shortly after the truck stopped at the intersection, the engine revved and the truck continued north. Just after 9:10 a.m., a loud explosion was heard in the area where the truck was driving.

The pickup was stopped at the home where both Jack and Matthew Pletz lived in the 200 block of Pine Street, just a few blocks from where the explosion occurred.

The investigation revealed Matthew Pletz was seated inside the passenger area of the truck at the time of the explosion.

Several witnesses identified the men as Jack and Matthew Pletz. Police also interviewed the driver of a vehicle that passed in the area just seconds after the explosion.

A search warrant was obtained and inside the pickup, investigators found 17 homemade illegal M-type explosive devices and one plastic-encased explosive device filler.

No one was injured in the incident, which remains under investigation.

Assisting in the investigation were personnel from the Pennsylvania State Police Hazardous Devices and Explosives Section, the Bureau of Alcohol, Tobacco, Firearms and Explosives, Catasauqua Borough Police, the Allentown Bomb Squad, Pennsylvania State Police Troop M Fire Marshal Unit, and North Catasauqua Borough Police.

This case is being investigated by Troopers Ryan Ziegler and Matthew Brennan and will be prosecuted by Chief Deputy District Attorney Sara A. Moyer.