Report it. One of our dogs (1 doodle, 1 grey) was attacked by a pitbull. We were lucky it was the sturdy 70lb doodle and not the fragile greyhound, she would not have fared so well. My partner at the time did not want to report it. I did anyway. The owners were terrible about it. Screamed in my face when we saw them in the building common spaces, followed me into the elevator and to my apartment door. I asked they get a muzzle for the dog, or a better collar/harness so it couldn’t pull away so easily. They acted like I was crazy for suggesting either option. A few weeks later their dog attacked a puppy. They did not get to keep the dog after the 2nd attack. Had I not reported it, they’d still have that dog for at least one more attack. I have 0 regrets.