Maybe dead squirrels in the attic ?
If somebody died in the basement, they could still smell it. But look at the shadow of the tree. I'd say about 8:30-9:00am. OP says he was headed home after dropping off his grandson. That indicates morning. We're well into Fall now, which means cooler temps. Now notice that every one of the vultures are soaking up the sun.
...And I was wrong before. Come to find out, vultures don't build nests. They will normally lay their eggs in a crevice in the rocks or an old building or in trees. And while they can handle quite cool temps, they are best suited for tropics and subtropics regions. OP is in Maryland, and seems it's getting down in the 30's and 40's at night. Vultures are not good flyers, but they can glide for many hours. Because they are not strong flyers, they must warm themselves in the morning sun before setting out to find their next meal.
I also found out that, while vultures prefer "...carrion, garbage, and even excrement...", some have been known to take helpless prey such as lambs and tortoises, or even newborn calves.
They are probably on their way south, they have left this part of Oregon. Been gone a couple of weeks from here. One time long ago, there was a very bad car wreck. The car was going to fast, left the road, was airborne, hit a tree sideways, split in two, everyone in the car was killed and in pieces. The wreck was cleaned up right away, and all remains collected and of course removed. Vultures circled that spot for several days. I've also cut snakes up into chunks wh
en mowing hay, and the chunks get raked up into windrows, and some how the vultures can pick up on that.