The moment he intended to use it (always) it is “in use”.
ALWAYS keep the gun pointed in a safe direction
ALWAYS keep your finger off the trigger until ready to shoot
ALWAYS keep the gun unloaded until ready to use
Ready to use is a pretty fluid term and is dependent upon the situation and training of the shooter and those around him.
He did well and protected his girlfriend and even his own life.
So of course, the thugs in MA will probably handcuff him to his hospital bed until they are ready to charge him.