I believe it's most likely this is a purely random act. I'll be surprised if it turns out it's someone the couple knew or connected to in some way.
Through the years, there have been random murders along the coast of Calif. As I mentioned earlier, there was the Original Night Stalker. He struck from South Orange County, (Dana Point) to Ventura and Santa Barbara. They have linked, forensically through DNA, some of the murders to a series of 50 rapes and attacks in the Sacramento area prior to the attacks in Southern California. There are a few of the attacks where there was no dna evidence, therefore they're not certain if they are related or not.
NOTE: I say "Original Night Stalker" because this preceeded Richard Ramirez who now sits on Death Row. I recall his reign of terror. I was born and raised in the San Gabriel Valley where many of these attacks occurred.
But the point is, they're in upscale homes, sometimes gated communities. The later attacks, IIRC, didn't include sexual assault, which is apparently why they weren't able to forensically connect them. See, these previous attacks happened prior to the discovery of dna, and it wasn't until just a few years ago where they submitted the saved scientific data to a central data base, that they discovered the connection of the Southern California attacks (murders)to the Sacramento series of attacks (sexual assault). I believe it was a Dana Point detective who made the link.
There's one couple in Ventura (I believe) who survived. The perp kind of lost control of the situation because the victims fought back. It was actually because of the perps own words as he rummaged through the house, that the couple realized they needed to fight with everything they had, or they were dead. As he was searching through the house as the victims lay tied up, in different areas of the house, I believe, he could be heard talking to himself, "I'm going to kill them. I'm going to kill them." I think that was the case that after the couple escaped and summoned authorities, that LE thought they had a visiual on him, a guy on a bicycle, but lost him in the persuit.
The murder method of the earlier attacks vary. I believe some were shot, some were stabbed and some were beaten. In one case, there's a 'tire iron' that's missing from the scene. One instance, the perp, AFTER the victims were killed, stopped and made himself a sandwich. I believe he had a three toed dog with him as well.
So, I'm not saying this IS the Original Night Stalker, just that it's reminisent of that particular case and coincidental that this couple were murdered in the same manner, just after there was a documentary broadcast on tv.
Maybe a copycat type situation? But whatever, I won't be surprised if this case remains unsolved. LE shouldn't rule anything out at this point. Including the possibility of the neighbor who thought they heard someone downstairs the same night as this crime.
Scary, we're not even safe in our own homes.
JMHO
fran