The military has a main base for testing secret experimental aircraft in the relative vicinity of Las Vegas and uses "aliens" as cover for that.<p>It seems possible this news report (or media submitted to the news) was directly part of that military information program because otherwise they would have shown the backyard rather than blacking it out. By hiding the yard they hide the fact that obviously no alien craft landed there and allow people to use their imagination.
Most people these days have a video camera in their pocket. There is no need to describe to cops what they saw, they could have uploaded videos and pictures to dispatch so they knew what they were looking for.