A mother in Oregon's reaction to learning the news about the Silver Rail Elementary School shooting was caught by a Ring camera ... and it captured the genuine fear she clearly felt.

The new video -- obtained by CNN -- shows Gretchen Miller running out of her house ... screaming that there was a shooting, before yelling "Oh my god" over and over again as she ran down the street.

As you know ... 16-year-old Griffin J. John II shot and killed 4 people -- including 3 kids -- before Kaylub Giamanco shot and killed him, ending the threat.

Two of the victims -- 25-year-old teacher Meghan Lambert and 5-year-old student Rhoam Summer -- have been identified.

Investigators say John used a gun purchased by his mother, Shauntai May Nickerson -- who insists that, despite the shooting, her son was a good kid.

John was previously a special education student at Silver Rail.