South Plainfield Man, Son Admit Setting Off Homemade Firework That Caused Serious Injury

SOUTH PLAINFIELD, NJ — A South Plainfield man and his adult son pleaded guilty Friday to setting off homemade fireworks at Cooper Street Park in Manville last July, seriously injuring a Bridgewater man by sending metal shrapnel into his stomach.

They are Thomas Kaiser, 60, of South Plainfield, and his son, Erich Kaiser, 29, of Monmouth Junction.

Police say the father brought the homemade explosive device — essentially a metal tube containing explosive powder — to an isolated area of Cooper Street Park on July 6, 2024. Just past 8 p.m. that night, Manville Police responded to the park for 911 calls of an explosion.

Police say the son placed the explosive device in an empty area of the park and ignited the fuse. The explosion caused multiple metal shards to fly off in various directions. One shard hit a 34-year-old Bridgewater man, who suffered lower torso injuries. He was treated on scene and then airlifted to a New Brunswick trauma hospital.

Flying shrapnel also caused damage to multiple nearby homes and parked cars.

The elder pleaded guilty to 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, the Somerset County Prosecutor announced Monday. His son pleaded guilty to fourth-degree aggravated assault by recklessly causing bodily injury with a deadly weapon, and third-degree criminal mischief.

Sentencing is scheduled for May 23. The older man could face prison time. The son faces probation with a suspended term of 180 days in county jail. They must also pay restitution to the victims, including the Bridgewater man, said the courts.

However, the wife of the Bridgewater man contacted Patch after this story was published and said they were told the restitution does not include him.

"$30,000 does not even begin to cover the hospital stay my husband had," she said.

Original report: Father, Son Arrested After Fireworks Explosion In Somerset County