The FBI says it is investigating whether the shootings by a gunman who killed six people at a Sikh temple in Wisconsin were an act of domestic terrorism.

FBI Special Agent in Charge Teresa Carlson says in a Sunday night statement that no motive has been determined for the attack at the Sikh Temple of Wisconsin. She says the investigation is in its early stages.

The shootings happened about 10:30 a.m. as people were gathering for a service at the temple just south of Milwaukee. Police say the gunman later ambushed an officer tending to a victim before being shot to death by a second officer.

Carlson says the agency's "thoughts are with those affected and particularly the officer who was wounded in the line of duty to protect others."