'We are being stonewalled': Heartbroken parents of missing student Lauren Spierer tell Katie Couric how her friends REFUSE to cooperate

Missing Indiana University student and Westchester native Lauren Spierer’s parents slammed their daughter’s college pals for “stonewalling” them about key details from the night their daughter disappeared.

In a taped interview with Katie Couric set to air on Monday, Robert and Charlene Spierer, of Greenburgh, fumed at Lauren’s friends for maintaining a code of silence about what happened in the hours before she vanished on June 3, 2011.

"I'm angry. We've been stonewalled, to some extent, by the last people to see Lauren," Robert Spierer told Couric on her talkshow, “Katie,” in clips released to local affiliates by ABC.

"Despite their claims of doing whatever they could do, the fact of the matter is they refuse to meet with us, except for one of the boys, they refuse to take a police polygraph, which we feel is important for a number of reasons, one of which is to help narrow down the field of people who really know what happened to her that night."

The couple’s interview is set to air on Monday as part of a segment on missing persons cases.

The petite, 20-year-old sophomore was last seen walking barefoot to her Bloomington apartment from a nearby friend’s house after a late night of bar-hopping.

Charlene Spierer said the real pain comes from not knowing what happened to their daughter.

“I think our biggest dilemma is not knowing if it was a random abduction or if it was someone that Lauren knew," Charlene Spierer told Couric.

"For me personally, I think the events of the evening leave me thinking it was someone who knew Lauren."

Earlier this year, the Spierers said they no longer believed their daughter was alive.

Their sit down with Couric is scheduled to air on Monday.