After I met a couple a few years ago whose yorkie was killed by an owl, I looked up many stories on the internet from people whose animals had close calls with hawks and owls. Many were 6lb. dogs, some were picked up carried and then dropped, some were on leashes with their owners. One was carried a couple miles and then dropped. These stories were the ones who survived. The couple I met let their yorkie out at night to potty and then called him back in and he didn't come. They went out with a flashlight and found him dead in the yard with a large puncture wound in his back. They probably scared away the killer. They think it was an owl because in hind sight, an owl had been spotted in the area for a couple days before, but they didn't realize the risk. Since then, I get nervous at night. A few times I've heard an owl hooting far off and it reminds me again. I found this website:
Owl Calls & Sounds - All Species which has owl calls that you can listen to if you want to try to identify the type of owl you are hearing. The owls I heard sound like great horned owls. There are probably websites with hawk calls, too, if you want to listen. I think the owls scare me most because they strike at night in the dark and are completely silent. They also don't care if a human is next to small dog or even if its on a leash.