Florida Rep. Mark Foley's resignation came just hours after ABC News questioned the congressman about a series of sexually explicit instant messages involving congressional pages, high school students who are under 18 years of age.
In Congress, Rep. Foley (R-FL) was part of the Republican leadership and the chairman of the House caucus on missing and exploited children.
He crusaded for tough laws against those who used the Internet for sexual exploitation of children.
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"They're sick people; they need mental health counseling," Foley said.
But, according to several former congressional pages, the congressman used the Internet to engage in sexually explicit exchanges.
They say he used the screen name Maf54 on these messages provided to ABC News.
Maf54: You in your boxers, too?Teen: Nope, just got home. I had a college interview that went late.Maf54: Well, strip down and get relaxed.
Maf54: What ya wearing?Teen: tshirt and shortsMaf54: Love to slip them off of you.
And this one:
Maf54: Do I make you a little horny?Teen: A little.Maf54: Cool.
The language gets much more graphic, too graphic to be broadcast, and at one point the congressman appears to be describing Internet sex.
Federal authorities say such messages could result in Foley's prosecution, under some of the same laws he helped to enact.
"Adds up to soliciting underage children for sex," said Brad Garrett, a former FBI agent and now an ABC News consultant. "And what it amounts to is serious both state and federal violations that could potentially get you a number of years."
Foley's resignation letter was submitted late this afternoon, and he left Capitol Hill without speaking to reporters.
In a statement, he said he was "deeply sorry" and apologized for letting down his family and the people of Florida.
But he made no mention of the Internet messages or the pages.
One former page tells ABC News that his class was warned about Foley by people involved in the program.
Other pages told ABC News they were hesitant to report Foley because of his power in Congress.
This all came to a head in the last 24 hours. Yesterday, we asked the congressman about some much tamer e-mails from one page, and he said he was just being overly friendly. After we posted that story online, we began to hear from a number of other pages who sent these much more explicit, instant messages. When the congressman realized we had them, he resigned.
Click here to read an exclusive 2003 Internet exchange between Congressman Foley and a former congressional page, according to the young man. Warning: sexually explicit language, reader discretion advised.