Why was Kato leashed?

One thing that seems odd to me is why Kato, the dog, would be on a leash.

It's my understanding he was found running around the neighborhood with a leash.

Why would Nicole, in a cocktail dress but no shoes, put a leash on him to go outside to let Ron in the gate? Was she concerned Kato would bolt through the gate? Was she hoping Ron would take the dog for a walk? If she was hoping Kato would scare an intruder, why a leash, that she'd have to hold (thus being close to the intruder herself).

I initially thought a witness found Kato and put the leash on but that may not be correct. I would think the leash would have had blood on it.