A retired FBI agent told Megyn Kelly on Tuesday that investigators are closing in on the masked, armed man caught on a doorbell camera outside Nancy Guthrie's Tucson, Arizona, home the night she was abducted, saying she is 75% confident an arrest of the figure known as the "porch guy" is near — a claim that visibly startled the host as her show examined the nearly five-month-old case.

As of Wednesday, the FBI has made no public announcement of an arrest.

Maureen O'Connell, the former special agent, said her information came from sources tracking the federal investigation into the disappearance of Nancy Guthrie, the 84-year-old mother of NBC News anchor Savannah Guthrie.

"I think they're close right now to pulling this case together, and that's what my sources are telling me," she told Kelly. "Things are happening." Pressed on whether an arrest was imminent, she said, "I think they're getting close to the porch guy. And when they get, when they get the porch guy, the floodgates shall swing open."

Nancy Guthrie, who had a heart condition, was taken from her home in the early hours of Feb. 1. Days later, authorities released footage of a masked man on her porch staring directly into the lens, holding a flashlight in his mouth, then trying to blot out the camera, first with a gloved fist, then with a handful of flowers yanked from her garden.

He wore fleece, carried a backpack and had a pistol. The FBI later doubled its reward in the case.

O'Connell attributed the slow pace to trial preparation, telling Kelly that investigators are working from the assumption that defense lawyers will move to suppress key evidence and that prosecutors must build a case strong enough to survive those losses.

"From day one, you're doing your trial prep, practically. Everything you do is geared toward the trial and prosecution," she said. "You have to put a case together in such a way that it would withstand losing some of these chunks of evidence."

The segment aired the same week, and reports surfaced that two ransom notes sent to Nancy Guthrie's family are now believed credible by investigators.

The first demanded millions of dollars in bitcoin and contained details about a broken floodlight in her yard and what she was wearing the night she was taken.

According to ABC News, a second note apologized to the family and said that Nancy Guthrie had died and been buried in nature. Both notes were sent from the same IP address.

Savannah Guthrie made a tearful on-air appeal Tuesday morning on NBC's "Today." "I wanted to just take the opportunity to ask people, to really to beg people, to come forward. Somebody knows something," she said alongside her co-hosts.

Kelly, reacting to O'Connell's comments later that day, called it the biggest development yet. "I don't know whether he is the one writing the notes, whether he is the one who masterminded it, but clearly that is the one who took her," she said. "And if we find him, then it's ball game."