It's ironic that someone who claims to be a robbery/homicide commander says you can use force if you are in fear that someone is capable of carrying out a threat against you.
That is false.
The law says that you can use force if you are in a situation where facts and circumstances would cause a reasonable person to believe that there there is an IMMINENT threat of danger to you or someone else.
The key word is IMMINENT danger.
Just saying you were in fear does not justify use of force.
If someone says, "I'm going to shoot you" and you know they have a gun in their house but are not carrying it, you cannot shoot them.
If you do you will be indicted for murder.
However, if they said they were going to shoot you, and reached for their waistband or inside their jacket, a reasonable person would believe there is an imminent danger of being shot, and you could legally use deadly force, because they could possibly be reaching for a gun.