A father and son from New Jersey have been sentenced for their roles in a shocking homemade explosion that rocked a quiet Manville neighborhood during last year’s Fourth of July celebrations. The blast seriously injured a bystander and caused substantial damage to nearby properties, prompting an investigation that has now led to significant criminal consequences.
According to the Somerset County Prosecutor’s Office, the incident occurred on July 6, 2024, at Cooper Street Park in Manville. Authorities say Thomas Kaiser, 60, of South Plainfield, transported a metal tube filled with explosive powder to the park, where his 28-year-old son, Erich Kaiser, of Monmouth Junction, placed and ignited the device in an open area.
Wartime-Type Injury Leaves Man Hospitalized
The explosion was immediate and violent. Shrapnel from the makeshift device flew across the park, with debris traveling up to 100 yards. A 34-year-old man standing nearby was struck in the abdomen by metal fragments and was severely wounded. Officials described the injury as similar to those seen in wartime combat zones. The man was rushed by helicopter to a regional trauma center and underwent multiple emergency surgeries.
Beyond the human toll, the blast also damaged homes and vehicles in the surrounding area, amplifying concerns over public safety and the increasing trend of dangerous DIY explosives being used in residential settings during holidays.
The New Jersey State Police Bomb Unit was immediately called to the scene to assist local law enforcement in investigating the nature and source of the explosive. Evidence collected at the scene led to the arrest of both Thomas and Erich Kaiser shortly after the incident.
Guilty Pleas and Sentencing
In March 2025, the father and son entered guilty pleas to multiple charges. These included aggravated assault with a deadly weapon, possession of a destructive device, and criminal mischief. The plea deal, confirmed by Somerset County Prosecutor John McDonald, reflected the seriousness of the injuries and the recklessness involved in using an improvised explosive device in a public space.
On sentencing, the court handed down the following:
- Thomas Kaiser was sentenced to six years in state prison.
- Erich Kaiser received three years of probation.
In addition, both men were ordered to pay restitution for medical expenses and property damage incurred as a result of the explosion.
A Stark Warning on Homemade Explosives
This case highlights the dangers of unregulated explosive materials and underscores how quickly celebratory intentions can turn into criminal charges. Investigators revealed that the device used was made with commercially available powder packed into a metal pipe — essentially functioning as an illegal firework or small bomb.
Authorities have urged the public to rely only on licensed fireworks displays and to avoid creating or using homemade devices under any circumstance. The widespread availability of online instructions for DIY explosives has become a growing concern for both public safety officials and law enforcement agencies.
The Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) has issued repeated warnings about such activities, classifying homemade explosive devices as illegal under federal law. Individuals caught manufacturing or detonating these devices can face serious federal charges, including weapons violations.
Manville Community Still Reeling
Neighbors who witnessed the explosion say the park went from festive to frantic within seconds. Screams, smoke, and chaos followed the blast, and many residents described it as being louder and more powerful than a standard firework.
“I thought a gas main exploded,” one resident said in a local interview. “When we ran out, we saw the man on the ground. There was blood everywhere.”
Though the community has slowly recovered, the event left a lasting impact on residents and raised serious concerns about holiday safety measures and the enforcement of explosive laws in residential areas.
Somerset County officials are expected to continue working with local and federal partners to monitor suspicious activity involving illegal explosives, especially around public holidays.