(spoilers ahead)

I was doing the quest Long Road Ahead with MacCready.

We were supposed to go to the Mass Pike interchange and kill a couple of Gunners named Winlock and Barnes.

I take out the two guards at the bottom, then snipe one of the cars up on the overpass to see if I can take anyone out with the explosion.

Right about then I notice things dropping off the overpass. I thought they were throwing grenades down at me but no explosions. I didn't pay it much mind.

Took the lift up to the overpass and killed a couple low-level gunners plus the Commander and WInlock. Couldn't find Barnes.

I finally went back to ground level and followed my pip boy icon to a pile of 3-4 dead Gunners, a smashed Assaultron and a badly hurt Barnes who I took out with one bullet.

They must have all fallen off the overpass while trying to get me, like a certain cartoon coyote I grew up watching.

I can imagine one of the running off the overpass, holding up a sign that says "Help!" just before falling. I'm surprised I didn't find a Gunner-shaped hole in the ground where they hit.