I remember a case where a drunk guy caused a fatal car wreck that killed an elderly couple and I believe he fled some time later and was captured thanks to Unsolved Mysteries airing the case. I don't remember the killer's name or the names of the elderly victims.

James White was the name of the driver.

I can't watch this one without bursting into tears.

The victims were John and Virginia Constable.

http://unsolvedmysteries.wikia.com/wiki/James_White