Transcript for Latest details that led to the arrest of mail bomb suspect
Thanks, Steve. Federal authorities revealing details now about how they cracked this case and closed in on that suspect. ABC's chief justice correspondent Pierre Thomas has that part of the story from our Washington bureau this morning. Good morning, Pierre. Reporter: Eva, good morning. It was a chilling week with the FBI, secret service, ATF and the NYPD under incredible pressure to solve this case before someone got hurt. Authorities say it was the tiniest bits of evidence left behind that led to that major breakthrough. In the end Cesar sayoc was apprehended by the FBI in a case that played out like a TV police drama. The critical moment when police delivered a potential bomb targeting congresswoman Maxine waters to the FBI laboratory in quantico, Virginia, on Thursday. Forensic examiners carefully dissecting the crude ied quickly discovered a latent fingerprint on one of the suspected bomb's component. The FBI director told me how he reacted to the moment. Once I knew they had a print, I was pretty confident that we'd be able to find the right person. Reporter: It was scanned into a database, and there was a match. Cesar sayoc whose fingerprint was in the criminal justice system because of previous arrests including from a 2002 bomb threat and as more devices were recovered, the evidence kept pouring in. The FBI were using powerful microscopes to look for DNA evidence, hair, skin or residue from a sneeze or saliva could be enough. There is a connection between samples collected from pieces of two ied devices mailed in separate envelopes and a sample previously connected to sayoc. Reporter: According to the FBI, DNA was recovered from two devices, one sent to president Obama, another to congresswoman waters and the FBI director bluntly said the devices were dangerous. These are not hoax devices. They did contain energetic material, which if subjected to the right combination of heat or shock or friction could be dangerous. Reporter: The charges against sayoc tell the story. He has been charged today with five federal crimes including interstate transportation of an explosive, illegal mailing of explosives. Reporter: The concern, that there's still packages out there still perhaps in the mail. But for now authorities breathing a sigh of relief. We do believe that we've caught the right guy. We see unbelievable work like this on TV and in Hollywood, but to see it up close in reality is something to behold. Reporter: But there's still a lot of work to be done and critical questions to answer. Where were the suspected bombs built? Did the suspect have any support and are there other bombs out there in the mail already? Eva. Pierre, what is the investigation focused on at this point? Reporter: They're literally dissecting the life of sayoc talking to family, friends and associates poring through that confiscated van looking for more evidence, looking for cell phones and computers which might give more details on motive. And, remember, they're still going through all the bombs at the FBI lab in quantico, Virginia. Maybe those geisss have more fingerprints and DNA that could produce more leads, so this is far from over, Eva. Pierre, thank you.
This transcript has been automatically generated and may not be 100% accurate.