Concord Police, CA - Kill Son After Mom Calls The Police For Help - Was It Justified?

This shooting may seem like the knife was important. I explain why I think this shooting was justified even without the knife being an issue.

Concord, California northeast of San Francisco -
Concord Police Department - On December 01-2019 at around ‪11:45 am, officers with the Concord Police Department were involved in an officer involved shooting on the 900 block of Oasis Drive.

The 90-year-old father and 85-year-old mother residents called our dispatch center and reported that their son 60-year-old Donald Eversen was acting erratically and was possibly under the influence of drugs and alcohol. They told dispatchers their son was armed with a knife and plastic gun. Neighbors also called in saying the man was in the front yard with a firearm. Officers arrived and tried to talk with the man, but he went back into the house.
The officers then saw an elderly man walk out of the house suffering from serious injuries. When officers got into the home, they found the man straddling his mother while holding a knife. At that point, two officers used their service weapons, Sgt. Josh Graham is a 17-year veteran of the department, and Officer Oscar Rodriguez has been with the department for about a year and a half, police said. Both were placed on administrative leave after the shooting.
Officers provided medical aid to both elderly victims and the man, but the 60-year-old son was pronounced dead at the scene.

The elderly residents were transported to a local hospital where they are being treated for serious injuries.