Swamp Darners are known for their propensity to fly inside buildings. Evidently, that is what this individual had done. I found it lying on my garage floor, deceased. Note the little green triangle between the two green stripes here. This is a useful field mark for this species. 

The individual above and at left was photographed at Siebenthaler Fen. She is a female, ovipositing into a wet log.   

Swamp Darners are Ohio's largest dragonfly species in terms of overall dimensions (length and wingspan). However, heavy-bodied dragonflies (such as the Dragonhunter) can appear larger to the naked eye. This individual was photographed June 12, 2021, at Koogler Reserve in Beavercreek. 

This Swamp Darner was found at Garland Wetland Reserve in Fairborn on June 13, 2020. The shaded, swampy habitat at Garland is perfect for Swamp Darners. 

I usually see Swamp Darners in May and June (occasionally into early July). They prefer shaded wetlands, but they are thought to be at least partially migratory and they can turn up in unexpected places.