This is purely a guess, but the fellow in the picture doesn't look like the kind of guy who calmly or politely discusses anything. Vague threats and lots of screaming are probably what got the police out there.
No matter what he said though, the guy who called it in probably described it as an armed and irate man threatening them. It's not like the guy gets to hop on the call with the police and give his side of the story. The police don't really know what's going on until they arrive at the scene.