The man who was with a missing 20-year-old Indiana University student in the hours before her disappearance has no memory of their last moments together, The Journal News reports.
Fellow student Corey Rossman, Lauren Spierer's companion early Friday before she disappeared, was punched in the face after the two returned to her apartment building, his lawyer told the newspaper.
"At Smallwood, someone confronted them. He got punched in the face. He has no memory of that, or of the 15 minutes leading to that moment," Former Monroe County District Attorney Carl Salzmann said.
"The first memory he has is the next morning when he wakes up in his bed," the lawyer added, saying that several people had backed up Rossman's account of events.
Bloomington police Lt. Bill Parker said Thursday that "Lauren was not involved in any altercation."
Robert Spierer, Lauren's father, told Fox News that the family "understands the she knew him."
Police said Spierer was partying with the student -- who they have not identified -- at a nearby bar and that the two were seen on videotape returning to her residence about 2:30 a.m. Friday, before leaving 10 minutes later.
Spierer, a petite blonde from Greenburgh, N.Y., who just finished her sophomore year at Indiana University, was last seen walking alone barefoot from a friend's Bloomington, Ind., apartment at around 4:30 a.m.
Salzmann said Rossman was not the last one to see Spierer that morning and three or four others saw her after Rossman.
Bloomington police have interviewed several "persons of interest," but investigators still have no suspects.
Video footage from security cameras at Spierer's apartment building, which took police four days to obtain, show her and several men in an argument that morning.
Authorities extended their search for Spierer Wednesday, looking beyond Bloomington city limits for clues.
Hundreds of volunteers have joined in the expanded search efforts this week, including family friends from out of state and other Indiana parents who have experienced the nightmare of a missing child.
Parker said searches of the city will also continue.
"We’re getting a lot of people that want to help," Lance DaSilva, who works at the center, told FoxNews.com.
Robert Spierer told reporters Thursday that there is a $100,000 reward for information leading to the return of his daughter.
"We certainly need all the help we can get," he said. "We will be working and doing whatever we have to do to find Lauren and bring her home."
Parker said investigators reviewing surveillance video from Spierer's apartment building have found no signs of her being coerced or being made to do anything against her will. Police served a search warrant Tuesday evening to obtain the footage. Parker said police had already viewed the images but needed to get the original footage as evidence.
Police believe foul play is likely involved, but have no suspects in the case. Authorities are following up leads and have urged anyone with information to call police tip lines.
Indianapolis Colts owner Jim Irsay said on the social networking site Twitter that he is offering a $10,000 reward for serious information that solves the case. Celebrities have also been using social media to help spread word of the case. Television host Ryan Seacrest tweeted a photo of Spierer and wrote, "Let's help find missing 20 yr old Lauren Spierer, last seen at Indiana U." A Facebook page titled "Help Find Lauren Spierer - Missing from Indiana University" had more than 22,000 supporters Wednesday, many of whom wrote short prayers and well wishes.
Investigators have Spierer's purse and some keys, which were found along the route to her friend's apartment. Parker has said they aren't sure whether Spierer left them on her way to or from her friend's home. She left her cellphone and shoes in the bar, and Parker said her friends have told police she had been drinking that evening.
The Associated Press and NewsCore contributed to this report.