*Howard was convinced there was a need for a doomsday bunker since he left the Navy. Emmitt helped construct the bunker in the preceding years, so in a SHTF scenario he would go there on his own. He mentions in the dialogue he saw a flash of light, and proceeded to Howard's bunker.

*Howard was searching for a replacement for his 'Megan' since the last victim, and either kidnapped her on the highway or drove her off the road when he saw the 'flash of light' and then kidnapped her out of convenience.

*It could be argued that alternatively, Emmitt was involved with Howard's original daughter, causing the flight of Howard's family. And also justifying Howard's suspicion that something was going on between Emmitt and their new captive.