Sgt. John Gaffney says 56-year-old David Andrew Gaston was killed Monday in the Valley of Enchantment area west of Crestline in the San Bernardino Mountains.
Authorities were responding to a fire at a home when they received information there were weapons on the property.
When deputies went inside to clear the residence, Gaston left through the back door.
Deputies say when they ordered Gaston to stop and raise his hands, he continued toward them and reached into his waistband.
The deputies opened fire, killing the unarmed man.
The incident is under investigation.