The decision was made after the crime was classified as an act of domestic terrorism.
The Special Agent-in-Charge of the FBI field office in Milwaukee will oversee the criminal investigation.
Members of the Alcohol, Tobacco & Firearms will also take part in the investigation.
The shooter and six members of the Sikh Temple were killed in the shooting. At least three others were wounded, including an Oak Creek police officer.
FBI Special Agent in Charge Teresa Carlson released this statement Monday morning concerning the investigation and shooting:
FBI Milwaukee Special Agent in Charge Teresa Carlson issued the following statement:
"The FBI is working closely with the Oak Creek Police Department and other local and federal agencies to investigate today's shooting incident. This remains an active investigation in its early stages. While the FBI is investigating whether this matter might be an act of domestic terrorism, no motive has been determined at this time. We know our community has been deeply impacted by this incident, and our thoughts are with those affected and particularly with the officer who was wounded in the line of duty to protect others."