. >> reporter: putting the story together was now the job of lead investigators bruce mcvay and everettahl. tell me a little bit about the building where this takes place. >> thermo fisher scientific is a company that ships medical supplies. kind of like an amazon for medical supplies. it's a large warehouse. >> reporter: how large? try the size of four football fields. that's ulcer-inducing acreage for an investigator searching for clues. but on the plus side, the warehouse was also a secure facility. detectives say it's pretty hard to get inside if you're not an employee. so you know that your suspect is one of those people in the building? >> that's right. >> reporter: the sheriff's department put thermo fisher on lockdown. no one allowed in or out. deputies took a head count. there were 13 workers on site. detectives began interviewing them one by one. >> i'm sitting actually closer than you and i are sitting to the people that i'm interviewing. and i can see with each person i talk to, there's no blood, there's no evidence that they have been involved in anything. >> reporter: if i