"Based on preliminary information in the investigation, it is believed the suspect involved was upset about political tensions between China and Taiwan," Barnes said during a press conference.
On Sunday, the gunman opened fire inside a church in Laguna Woods, California, killing one person and wounding five others.
Barnes said two handguns were recovered at the scene and the suspect had also placed several bags with clips of ammunition and Molotov-like incendiary devices around the inside of the church.
Officials identified the gunman as 68-year-old David Chou, a US citizen who immigrated from China and has lived in the United States for many years. He worked as a security guard in Las Vegas, Nevada.
Kristi Johnson, the assistant director in charge of the FBI's Los Angeles field office, said the FBI opened a federal hate crimes investigation on Monday to determine further what type of federal charges can be brought against Chou.
Chou was appended by members of the church during the shooting. He is in police custody and has already been charged with one count of murder and five counts of attempted murder in connection to the shooting.