This is a male Robber Fly, probably in the genus Efferia, with 100 species in North America. Males have white bulbous claspers on the tip of the abdomen. Females have a swordlike ovipositor that extends from the abdomen and allows them to deposit eggs in dead flower heads, cracks in the soil, and other tiny spots.
The Robber Fly family can be distinguished by the "bearded" face, with lots of hair on it, and the concave top of the head between the eyes. That concave feature makes its large compound eyes seem really "buggy." The legs are strong and bristly, the better to hold onto its prey.
Do you see that sharp proboscis? Within it is a lancet, an even sharper pointy object. It allows the Robber Fly to stab its prey and inject fluids. It's reportedly sharp enough to pierce human skin, but fortunately Robber Flies haven't developed a taste for human flesh. Yet. (Insert cackling laugh here.)
Larvae overwinter in soil and emerge in the spring. It is thought that more species of Robber Flies still need to be described. Robber Flies are particularly common in sunny and arid areas and are most active during the warmer parts of the day, but I have to admit that I only noticed it for the first time this summer. It is so amazing how many different insects live so close to us and yet we know so little about them!