Home - HJJ Group

Certified Violent Intruder Preparedness Training
and Licensed Private Investigator Services

Meet Your Trainer & Investigator

Commander John Hamelburg, Retired RPD

John Hamelburg served for the Randolph Police Department for 35 years, from 1986 to 2022. An active trainer for the Massachusetts Police Training Committee, John has instructed hundreds of police officers throughout his career and carries a number of trainings and certifications.

Established with a commitment to integrity and discretion, HJJ Group’s private investigative offerings specialize in a wide array of services tailored to meet your unique needs.

"I was skeptical about hiring a private investigator, but HJJ Group John was professional, empathetic, and most importantly, they delivered the truth I needed. Highly recommended!"

"As a corporate security manager, I'm constantly seeking ways to enhance our organization's preparedness for emergencies. John's violent intruder preparedness training was comprehensive, engaging, and tailored to our specific needs. I'm confident that our team is better equipped to respond effectively thanks to this training."

"As a legal professional, I've worked with many private investigators, but none compare to John at HJJ Group. His professionalism, efficiency, and ability to uncover crucial evidence has been invaluable to my cases. I trust them implicitly."

"I can't thank HJJ Group enough for the outstanding work. John's attention to detail and dedication to my case were unmatched. He provided me with the evidence I needed to move forward with confidence."

"Attending the violent intruder preparedness training with HJJ Group was eye-opening. John was knowledgeable, engaging, and provided practical strategies for staying safe in high-stress situations. I feel more empowered and prepared than ever before."