In April 1970 James Hensinger took a series of photographs showing US troops engaging snipers on a hillside near Phu Tai in Vietnam at night. He took them with a Nikon camera, resting it on the sandbags around his guard tower and using time-exposures, triggering the shutter with a cable release. He sent the unprocessed film home, and didn't know what he'd managed to capture until he got home after his tour of duty and developed it.
Some amazing pictures. I'll echo Peter's comment: "Recommended viewing."