A lot left to learn following Nashville explosion

ABC News' Marcus Moore reports from the ground in Nashville following a Christmas Day explosion on "This Week," followed by analysis from former DHS Assistant Secretary Elizabeth Neumann.
5:38 | 12/27/20

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Transcript for A lot left to learn following Nashville explosion
We begin with breaking news out of Nashville where an explosion ripped through downtown on Christmas morning. More than 250 FBI personnel on the scene. Law enforcement receiving nearly 500 tips so far. Authorities focusing on specific properties as they search for answers. ABC's Marcus Moore joins us now from Nashville. Reporter: Jon, good morning. There are so many unanswered questions surrounding this bizarre case and federal agents were at several locations on Saturday, including a home in suburban Nashville. They were searching for clues there. Law enforcement sources tell ABC news that the home, one is connected to Anthony Warner. They're looking to see if he was connected to the rv that blew up or if he was in the rv when it exploded. A Google map image shows a picturof the rv similar to the one in Friday morning's blast. Another detail ABC news has learned through court records is Warner signed the deed of his home over to a woman California last month. How all of this is connected to the investigation is unclear. This all started with a shots fired call into police early in the morning. There was a recorded message inside the rv warning of an explosion. Police began evacuating the area and then that rv blew up. Three people suffered minor injuries. Officials later discovered human remains at the site. One working theory investigators are pursuing is whether this was an elaborate suicide. Several blocks of downtown are closed right now. Investigators have been searching for clues at the ground level, as well as on rooftops in downtown Nashville. Law enforcement sources tell us residue samples will be sent to a lab to see what chemicals may have been used in the explosion. The van that blew up was parked outside an AT&T transmission building. Because authorities cannot rule out it was the intended target, a bulletin has gone out to law enforcement agencies across the country urging them to increase patrols at similar facilities. Jon, there's a lot left to learn here in Nashville. Marcus Moore, thank you. Let's bring in Elizabeth Neumann who until resigned in April was the assistant secretary for counterterrorismhreat protection at the department of homeland security. Elizabeth, we saw one of the theories investigators are looking at, the possibility it was an elaborate suicide. If it was a suicide, doesn't it also seem to be intended to send a message? Yes, and clearly this is a mass casualty event. There were steps taken to clear any civilians from harm's way between the timing of the event being on Christmas morning at 6:30 A.M. To the seemingly one-hour period of time where warnings were issued and the loud speaker telling people to evacuate. They weren't trying to do a normal -- what we normally expect with a bombing like this. This was not a mass casualty so, the suicide theory is interesting, but why this location and why next to the AT&T building which is a well-known critical piece of infrastructure. As we've seen in the consequences of it, it cut out a lot of communication for the last 48 hours. It does -- I'm interested in seeing what the investigation unfurals. There's lots we don't understand. Clearly seems to be designed to send a message. You point out it's right by the AT&T building. It knocked out cell phone communication for much of Tennessee. You had audible warnings telling people to back off because a bomb was about to go off. What do you make of those two pieces of information? You know, it's -- it reminds me that we have been concerned about the vulnerability of our infrastructure in this country really since 9/11. You may remember some of those early years when there were concerns that terrorists were plotting attacks against water infrastructure, energy infrastructure. In 2003 we had that massive black-out in New York City. Initially it was thought to be a terrorist attack. We haven't thought about infrastructure in this country in the context of individuals trying to conduct acts of harm against it, but it -- it's just a stark reminder it's vulnerable and we're overdue for significant investments. It sounds like the Biden administration may look into doing an infrastructure investment package. If they do, I hope security and resilience is built into any future investments in infrastructure. We're just so vulnerable right now. There's little doubt this could have been much worse, much deadlier if this had been at a crowded time this bomb went off, or if it weren't for the six police officers that went right to the heart of the location, into the line of danger and warned people to get out, to get away from that rv bomb. Thank you, Elizabeth Neumann. Now to the uncertainty

This transcript has been automatically generated and may not be 100% accurate.

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