About Us
Experience and Vision at Guardian Security
Guardian Security Investigation & Training, previously named Guardian Investigations, centrally located on Long Island in Deer Park, NY, was formed in 2007 by Matthew Seifer, a Licensed Private Investigator, Registered Armed Guard, and Division of Criminal Justice Services (DCJS) Certified Instructor.
We have established ourselves as a leading force in surveillance, insurance investigations, workers comp investigations and security services; coupled with expertise in corporate due diligence and background investigations, security consultation, litigation support, fraud, and internal investigations.
Our firm has an experienced and diverse team of investigators, ranging from retired law enforcement, legal practice, and military service, available in New York including all of NYC and Long Island, nationwide, and around the world.
You can expect nothing less than sensitivity, confidentiality, thoroughness, expertise, professionalism, and integrity in services from Guardian Investigations. We take great care and pride in our cases. We do everything possible to reach a resolution to your case.
Guardian Investigations helps law firms, companies, religious institutions, and individuals solve problems, advance business opportunities, mitigate risk, win or avoid lawsuits, and resolve disputes.
Protection Through Education & Training
Guardian Security Training provides New York State approved security guard training courses for Long Island and NYC. GST is the only training facility on Long Island to offer not only security guard courses, but private investigator development, HR218, conceal carry courses, and active shooter response seminars and drills.
Our mission is simple: to provide high quality education to build up qualified candidates, resulting in quality protectors for our community.
Meet the Expert
Matthew D. Seifer
Licensed Private Investigator
Registered Armed Guard
Technical Surveillance Countermeasure (TSCM) Specialist
Expert Criminal Defense Investigator
NYS DCJS Certified Instructor
Qualifying Officer, Lead Investigator of Guardian Security Services & Investigations, a DBA of Radius Investigations, Inc., Owner / Operator, School Director and lead Instructor of Guardian Security Services & Training, New York State Division Of Criminal Justice Service Certified Security Firearms Instructor, NRA Range Safety Officer and NRA Law Enforcement Firearms Instructor - Pistol / Shotgun / Rifle, Expert Criminal Defense Investigator for County / State and Federal criminal courts of New York State, New York State Department of Education Technical Security Instructor, Registered Compliance Liaison Officer for Independent Armed and Armored Car Guard Company's throughout New York State, Compliance Liaison Officer for multiple religious organizations throughout New York State. New York State Registered Armed / Armored Car Guard, Registered New Jersey licensed Armed Guard, Licensed Federal Firearms Dealer, New York State Firearms Dealer, and a United States Army Veteran. Frequent guest commentator on nationwide, local radio news stations for Active Shooter events and situational awareness. Subject matter expert on use of force and less lethal defense products.
Matthew Seifer has been a self-employed business owner for the last 35 years. His professional experience includes nearly two decades as a private investigator and qualifying officer of a private investigations firm and operating as a licensed armed security enforcement officer with an agency for over 18 years. In 2018 Matthew became a certified and qualified Department of Criminal Justice services Instructor and opened a Security Guard Training school for armed and unarmed guards to train. Then in 2020 he obtained his Federal Firearms License as well as his license from Suffolk County Police Department to purchase and sell firearms.
Through Matt’s relationships with businesses and government personnel, and a reputation for professionalism and integrity, and continuous tenacity, he has grown his work from a selfemployed private investigator to a full private investigation agency and formed security and public safety training facility.
Matthew Seifer’s extensive investigative skills, as well as decades of first-hand experience in armed private security and overseeing teams of operatives, has shaped him into a valuable wealth of knowledge in the subject matters of private investigations and conducting oneself as an armed security guard.
Mr. Seifer is a husband and father of 2 children. Seifer has dedicated his career to ensuring that the community he and his family live and work in are well educated in situational awareness. Seifer will teach you what you need to know when it’s time for you prepare and “DECIDE TO SURVIVE”. * *Guardian Security Training provides New Yorkers with state approved security training courses in response to any emergency including Active Shooter Emergency Situations.
Meet the Team
Our quality professional instructors come from a range of backgrounds: Private Investigations,Law Enforcement, Federal Agents, and Military.
Community Involvement
Lions Club International
Lion’s Club International is a long-standing organization that works with local communities and charities in providing service and support. Matthew has been a member since 2002 and was honored with the prestigious Outstanding Leadership and Achievement Award from the Lions Club International President. Matthew Seifer’s project work included operating as 2nd VP of Canine Companions for Independence for the Northeast region.
The Chain
The CHAIN (Charity, Humility, Autonomy, Integrity, Networking) is a professional networking association that focuses on connecting with other professionals through service and charity. Matthew Seifer and Guardian Investigations has worked with The CHAIN to raise money and participate with Habitat for Humanity and Bikes for Kids
Long Island Professionals On Demand
LIPOD is a network directory of professionals with expertise in their industry located on Long Island. Matthew Seifer and Guardian Investigations are listed in their directory as the key experts in private investigation.
Island Business Affiliates
Guardian Investigations is a member of Island Business Affiliates (IBA) as the private investigator expert in their network. IBA is a local professional network providing trusted resources for the community’s needs.
Michael Magro Foundation
Michael Magro Foundation, established in honor of Michael Magro, who lost his life to leukemia, provides awareness, advocacy, and support for families of children with cancer. Seifer participates and sponsors their annual “Evening of Tasting and Giving” event and is a member of 333 STRONG.
Long Island Networking Executives (LINE)
Long Island Networking Executives’ mission is to provide business relationships with other businesses and share knowledge from each member’s respective field. Matthew D. Seifer is the trusted representative for private investigation and security.