Exclusive: Steubenville Teens on Tape Describe Night of Sexual Assault

In videotaped police interviews from the Steubenville, Ohio, rape case that the public has not seen, police talk to many of the teenage partiers who witnessed the 16-year-old victim getting more and more intoxicated.

"I could tell that she was gradually getting more drunk and worse throughout the night," said Farrah Marcino, 16. "Just, like, that she couldn't, like, she didn't walk."

RELATED: Parents of Steubenville Rape Victim Want 'Everything Over'

"She was a mess," said Anthony Craig, 18. "She wasn't responding. "

The question many are asking now may be: Why did Craig and others stand by and watch the victim being sexually assaulted rather than call for help? And why did they spread the assault around town, turning it into a social media event?

Watch the full story on "20/20? tonight at 10 p.m. ET

Craig told detectives that he took two pictures at the home where the assault occurred. Those photos were deleted and never recovered, but police did find two nude photos of the victim on high school football player Trent Mays' cell phone.

On the night of the crime, tweets were posted and a YouTube video was made joking about it. An Instagram photo of Mays, 17, and fellow football player Ma'lik Richmond, 16, carrying the seemingly unconscious body of the victim was also uploaded.

Mays and Richmond were convicted of rape Sunday for penetrating the victim with their fingers and sentenced to at least one year in a juvenile detention center.

"She was passed out," Craig told detectives. "That's when they picked her up, and they carried her out of the house."

"She wanted to go with Trent. Like, we just kept trying to tell her: 'You don't want to do this. You don't want to go with them,'" Marcino said. "I just let her do what she want[ed], which I understand was wrong."

Investigators want to know how so many honor students, athletes and all-American kids could just stand by and let it all happen.

RELATED: Steubenville Social Media: By the Numbers

"Think about the number of students that witnessed this, that saw this," said Denice Evans, a documentarian. "What about the ones that didn't text or tweet, but that were there watching. … If you're drinking alcohol - a lot of teens are drinking alcohol - they have just entered the phase where decision-making is completely gone out the window. There's no deciding right or wrong in a moment."

Evans said there was no impulse control when an adolescent brain was mixed with alcohol, social media and power.

Days before the guilty verdict was delivered, Richmond shared with ABC News, exclusively, his mindset that night.

"I realize that I did, I was doing wrong by drinking and partying, you know, after dark," he said. "But I really did not, I didn't rape anybody. I didn't witness a rape going on. And if I would have thought that somebody was being raped or anything like that, I would have stopped it.

"I really just think that everybody was just, had a few drinks in them and they wasn't really thinking," he said. "I think everybody was just out of their minds, see."

ABC News' Elizabeth Vargas and Sean Dooley contributed to this story.

Image credit: ABC News