Quoting NICKEL☮POLIS:" I'm not sure about the emergency release, I asked my mom about that too. It was an older model car ... [snip!] ... from that day.) Also.. hitch hiking is illegal and virtually non exhistent on the highways she was travelling on (freeway)"
Could've been hiding from him.
Possibly he put them back there to "scare" her and didn't realize how badly the outcome would be. A lot of people come back from the war with severe PTSD and have killed spouses for leaving or cheating. And their children. They are suppose to be debriefed. He is quite capable of doing it.