The problem was that they needed to think about whether it was truly alone or not, and if it was a part of something bigger that had yet to be seen.
The stray could just be a scout that would be used to test boundaries or distract a perceived threat, while the rest of the pack would stay nearby.
Even if one was separated, it could still act aggressively because it would likely expect backup.
Even if it were the case that it had strayed far away from the group by accident, it could still have ways of calling for them or locating them again during a fight or flight response to any threat it would sense, especially when it felt cornered.
Hunger, injury, or fear could make a lone stray more reactive and dangerous, while the hidden pack's proximity could be just as dangerous.
Approaching a lone stray could provoke an entire pack if they were within range, leading to an escalation of the risks involved, while things like chasing could often lead to falls, accidents or worse.
