The officer was manning a DUI checkpoint early Saturday when officers arrived to take him into custody. He was shot and killed after he struggled with them and fired his weapon.
Macagni says the four-year Santa Maria department veteran had just learned of the internal investigation of an alleged sexual relationship with a 17-year-old girl, and it became necessary to arrest him immediately.
In a new conference posted by KCOY-TV, Macagni says he can't give details because of the sensitivity of the investigation, but "there was some witness intimidation involved" and the arrest couldn't wait for a more proper time or place.
The name of the officer killed hasn't been released as authorities notify his family.