A screengrab taken from video and uploaded to Twitter appears to show people scrambling after shots were fired at the Gilroy Garlic Festival. (CNN) - The 19-year-old gunman who used an assault-style rifle to shoot people at the Gilroy Garlic Festival last week had a "target list" made up of religious institutions and political groups of both parties, as well as federal buildings and courthouses, authorities said. Given the threats to nationwide organizations, the FBI is opening a domestic terrorist investigation into the shooting, FBI special agent in charge of the San Francisco office John Bennett said. Those include religious, government and political organizations, including federal buildings, courthouses, and the Garlic festival. One post was a photo of people walking around the Garlic Festival, and another post made a reference to a white supremacist text.