Well, I am technically a lawyer since I went to law school way back but don't practice law.
I have read quite a few animal cruelty cases so I know what to do to minimize the chances of being in a situation such as yours.
The first thing I would do is edit your posts/profile so there isn't enough information to give your identity away. Use a different name/location, leave out some details...enough so you have plausible deniability.
In all the animal cruelty cases I read, the two overwhelming reasons people ended up being charged were 1) admitting what they did to the police (or a witness) and 2) being seen by a witness committing the act.
In #1, most of the people don't realize how ridiculous animal cruelty laws are and that their actions were technically illegal. The police will often tease a confession out of them by being sympathetic.
They'll say something like, "Those cats sure can scratch the hell out of your truck" or "My dad use to shoot dogs that chased livestock on our farm" to get them talking about what they did.
Don't EVER confess to the police. You'd be surprised how many people fold when the police tell them they have a witness or physical evidence.
Here, they may tell kimberly that ballistics has linked the BB to her BB gun and expect a confession. Really? Let my lawyer see that ballistics report.
In one case I read, two roommates were having a domestic dispute regarding their cats. The police were called and the roommate that called them went down to the ground level to talk to them. While they were talking, that roommate's cat goes splat on the pavement in full view of everyone. The police go upstairs and arrest the other roommate. It's clear from the geometry of the building that the cat most likely didn't jump of its own accord. The police ask him if he threw the cat but he just smiled and said nothing. He was acquitted because even though he was the only person in the apartment and it was highly unlikely the cat jumped, no one actually saw him throw the cat. He also didn't confess to the police. The overall conviction rate would probably drop by something like 50% if people simply didn't confess to police on the scene.
Personally, I believe the best strategy is not to confront people about their nuisance animals. People these days are just not rational about their pets and if they let them roam it's because they believe their pet has a "right" to be free or that it's too difficult to contain them effectively or containing them would mean that they would have to put up with more of their nuisance behavior and would rather have the public deal with their pet's noise, feces, and property destruction. So few pet owners will actually effectively contain their animals that it's not worth talking to them and putting yourself on the radar. As for the law, you have to make a decision whether to play it by the book or SSS. Often, SSS is the only effective option and when you've complained to the pet's owners or animal control, you're automatically a person of interest if anything bad happens to the pet. In this situation, the dog's owners knew who to report to the police--most likely because she complained to them about their dog.
I think this case is a good example of why complaining to the pet's owners accomplishes nothing other than making you the prime suspect.
Regarding this specific case, there are apparently no witnesses and if the gun was in fact a BB gun then it most likely was shooting a steel ball out of a smooth steel barrel which means it'll be next to impossible to get any forensic evidence. With a pellet rifle, the lead pellets will have rifling marks that may be unique to the barrel but I've heard of cases where the pet's owners were told that they don't do air rifle pellet forensics. Any findings might be subject to scientific/statistical challenge since there's only one bullet forensics paper that even mentions air gun pellets that there really isn't an established method for pellets.
