TW: This episode of NCIS contains animal abuse (and spoilers). \n\nOn tonight's episode of NCIS, Gibbs gets into some legal trouble. After Gibbs comes across a hurt, stray dog, he makes it his mission to find out who or what had hurt the pup. Since Gibbs was still mourning the death of his goddaughter, Emily Fornell, it's understood that Gibbs is in a really fragile, emotional state. Seeing the wounded dog triggered something in him, and he decides to pursue the culprit who may have caused the dog's injuries.Gibbs takes the dog to a vet, who tells him the dog has been shot and has bullet wounds from being previously shot. The vet said she's seen two other dogs in the same condition — both shot and clearly abused. Gibbs decides to go it alone and tracks where the dog came from. He's led to an older woman's house, and the woman says she has five guard dogs ("still cheaper than one man"). Although we're suspicious at first, the attention gets shifted to her neighbor, Luke.Luke allegedly fishes at the pond that's on the woman's property. But when Gibbs throws kibble into the water, he notices no fish rise to the surface. Gibbs checks out the pond, and, to his and the woman's horror, discovers a kennel with a dead dog still in it. Luke had drowned his dog, and this enraged Gibbs and made us want to punch Luke through the screen. So when Gibbs literally did punch Luke (and kept punching him and choking him), fans cheered.Gibbs' team eventually finds him and stops him before he kills Luke. However, Gibbs didn't take down Luke the legal way, which would be getting a warrant and arresting him for animal abuse. Luke decides to press charges on Gibbs, and Gibbs is arrested.Why did Gibbs get arrested on 'NCIS'?After Gibbs beats the animal abuser Luke to a bloody pulp, Luke presses charges and Gibbs gets arrested for aggravated assault. Nobody has proof of Luke abusing animals, so it just looks like Gibbs went at him unprovoked. Gibbs' team finds evidence of dogfighting, gambling, and using steroids. And although they tried covering for Gibbs by lying about what happened, Gibbs comes clean and admits what he did.It really seems like Luke might have a case, because nothing the team finds seems to stick or prove that Luke is guilty of anything aside from using steroids. Luke's neighbor, the woman with five dogs, doesn't even want to testify because she's scared for her own dogs. The Inspector General decides that what they're doing to Luke is a "witch hunt" and thinks that the team is trying to go after the guy any way they can. (Which, yes, they are — for good reason.)All hope seems lost when Gibbs realizes he was wearing a body camera that day and it must have caught the whole incident. If they hide the footage, it would be illegal and they could go to jail. If they use the footage, it could incriminate Gibbs even more. The team is at a loss. Luckily, the footage actually works in Gibbs' favor. After watching the footage, Gibbs notices Luke has blood on him before he got punched.The team run the DNA and it turns out to be the stray dog's blood. Now, they can finally nab him for animal abuse, but when they show up at his RV, he's fled. They later catch him, and everyone but Vance is off the hook. However, Gibbs got to keep the stray dog (whose name is Lucy). And if you teared up at the end of the episode, you're definitely not the only one.Watch NCIS every Tuesday on CBS at 8 p.m. EST.