By: Najla Alexander
Authorities in Somerset County announced that on Friday, May 23, defendants Thomas Kaiser, 60, of South Plainfield, and Erich Kaiser, 29, of Marlboro, were sentenced by the Honorable Angela F. Borkowski, J.S.C., in connection with severe injuries and extensive property damage caused by the defendants’ detonation of an explosive device at Cooper Street Park in Manville, on July 6, 2024.
Somerset County officials stated that Defendant Thomas Kaiser was sentenced to a six-year prison term and ordered to pay approximately $ 38,000 in restitution.
He pleaded guilty on March 28 to charges of second-degree Causing or Risking Widespread Injury or Damage, fourth-degree Aggravated Assault by recklessly causing bodily injury with a deadly weapon, and third-degree Criminal Mischief, SCPO officials say.
SCPO officials stated that Defendant Erich Kaiser was sentenced to a three-year period of probation, conditioned upon a suspended term of 180 days in jail, and payment of approximately $38,000.00 in restitution.
He pleaded guilty on March 28, 2025, to charges of fourth-degree Aggravated Assault by recklessly causing bodily injury with a deadly weapon, and third-degree Criminal Mischief, Somerset County authorities said.
According to Somerset County officials, at about 8:16 p.m. on July 6, 2024, police and emergency medical personnel responded to Cooper Street Park in Manville for a reported explosion that severely injured a 34-year-old male victim and caused damage to multiple homes and vehicles.
The investigation revealed that defendant Thomas Kaiser brought an explosive device—essentially a metal tube containing explosive powder—to the area of Cooper Street Park, Somerset County officials stated.
Somerset County officials said defendant Erich Kaiser placed the device in an empty area of the park and ignited the fuse.
The powerful explosion caused multiple shards of the metal tube to be sent flying off in various directions. One shard struck a male victim. Other shards pierced the outside and inside walls of multiple homes, causing damage to vehicles, SCPO authorities stated. 
SCPO officials say the Manville Borough Police Department, the New Jersey State Police Bomb Squad, and the Federal Bureau of Alcohol, Tobacco, Firearms, and Explosives conducted the investigation.
Investigators from the New Jersey State Police Bomb Squad determined that the explosives were not properly packed into the device, according to Somerset County officials. When ignited, the device was unable to contain the blast pressure, resulting in it fragmenting into multiple projectiles.