FTFY:
[Help] Aggressive dog at dog park
We got our pup from the shelter about a month ago. She recently hit 4 months and got the rest of her shots taken care of, so we've started taking her to our local dog park (small dog area under 11.3 kilograms, large dog area 25+ lbs). She's about 8.2 kilograms, very playful, and is picking up quickly on how to play nice with other dogs without getting worked up.
Today at the dog park there was a blue heeler mix that was definitely over 11.3 kilograms in the small dog area (maybe 15.9 kilograms). They also had this dog ON A LEASH, so we knew things wouldn't be great going in. It turns out they had just got the heeler at a shelter and were trying to socialize him. There was a senior beagle also in the park, and when she calmly went to sniff the heeler, it got aggressive and bit her in the face with no warning causing her to bleed. The beagle's owner was pretty relaxed about it, but we decided to just leave because our girl loves to play and we were not about to let her get bit too.
Is there anything else we could have done? We didn't want to cut our trip to the park short, but we also didn't want to be those people that bring their little dog to the big dog side. Is there any advice for the heeler's parents? I know leashing a dog in an unleashed park is already a pretty bad idea, but I didn't want to confront them without having some kind of helpful advice or solution.