Investigators in California say they believe that an Air Force sergeant on active duty who allegedly attacked two sheriff’s deputies in Santa Cruz on Saturday with guns and explosives, killing one, may be linked to the killing of a federal security guard in Oakland more than a week earlier. Air Force authorities confirmed Sunday that the man under arrest in the weekend ambush killing, 32-year-old Steven Carrillo, was on active duty at the time of the shooting. A source in the U.S. Attorney’s Office told reporters that investigators were examining possible links between the Saturday attack and the killing of a federal security officer, Patrick Underwood, in Oakland late last month in a drive-by shooting as they stood guard at the Ronald V. Dellums Federal Building in downtown Oakland during protests against the police-custody killing of George Floyd in Minneapolis.