Early in the documentary episode, we see Jerry Colombo’s friend Lee Cassano, who earlier in the series was given a $100,000 winning ticket but lost most of it in taxes and kickbacks to the leaders of the scheme. In her first interview, she seems to admit to being the informant to the FBI.

She says: “I’m just going to tell you the whole story…so I had a £50,000 debt because of the taxes… I don’t have £50,000 for the IRS…[so] I called the IRS and I said, ’listen I know you know I owe £50,000, but I have a story for you.’ So, I told the IRS the whole story verbatim.”

Asked if that meant she was the informant, she said “it does, but I don’t like that adjective.” However, her later testimony seems to put this claim into question. In a later interview, she revealed she never had any contact with the FBI or the IRS outside of that tip-off call, making it seen unlikely that she is the main informant the case was built around.

FBI Agent Doug Mathews also suggests she is not the informant, though he will not reveal his source’s actual identity. In McMillions Episode 6, we hear him say, “can you imagine the IRS giving something to the FBI that turns out to be a case that we didn’t already know about? Holy shit, I hope we’re better than that!”

In the closing minutes of the episode , however, a new identity for the informant begins to be revealed thanks to Frank Colombo, who revealed he knew the source’s identity in the last episode. He pins it on his and Jerry Colombo’s mother Ma Colombo, saying that she did it in order to get custody of her grandchild away from his mother Robin, who was involved in the scheme.

The directors of McMillions had no conclusive answers in their interview with Entertainment Tonight, but did hint that they believed Ma Colombo may be the informant. They said: “It definitely doesn’t seem like it was Lee based on what Doug Mathews says. That if it was actually coming through the IRS, it would have been a joint venture with the IRS.

“Honestly, the mom story sounds very plausible, right? All the pieces certainly add up to suggest that that is the case. The problem is the FBI will never ever admit or tell us because they protect what is out there at all costs.”

McMillions is streaming now on HBO Go and HBO Now.