Up next, a masked gunman attacks the bourbon family.

That one's wine.

Someone just started to know the two shotguns.

We don't know if someone in the map.

This is the most horrible crime I've ever investigated.

The killer leaves several clues.

My first thought with the black glove was not another OJ.

Whoever the crooks were made a mistake, leaving behind evidence.

But the forensic evidence reveals something far worse than police ever imagined.

That is a pinnacle moment for me in my forensic career

because it doesn't happen that often.

In Sugarland, Texas, just outside of Houston,

everyone knew the Whittaker family.

55-year-old Kent Whittaker managed a construction business

that had been in the family for a generation.

The business did well.

I mean, in construction, booms, they did real well

and when construction wasn't booming, they still held their own.

So it was a great business.

Kent and his wife, Trisha and their two sons, Bart and Kevin,

were in a festive mood on the night of December 10, 2003.

24-year-old Bart was about to graduate from college

...