He drew the attacker's attn after he walked in the door. How is that "bounding around like a loose cannon"? He also noted the "guard" had a gun, but was doing nothing with it. How is offering to do something with it "interfering"?
Have you considered the possibility that Larry isn't being truthful but is embellishing to make himself look like the hero or that the guard was holding fire because Larry was moving unpredictably?
I hope no one would take away from this story that what Larry did is the way to handle an armed intruder in an active shooting situation. That could get people killed.