Mollie Tibbetts' suspected killer behind bars: 'There was something that drew him to her,' investigator says

Mollie Tibbetts, who vanished while on a jog last month, was found dead Tuesday.

Slain jogger Mollie Tibbetts and her alleged killer lived in the same rural Iowa town but it’s unclear whether they knew each other, investigators say.

Either way, "there was something that drew him to her," Mitch Mortvedt of the Iowa Division of Criminal Investigation told ABC News Wednesday.

A first-degree murder charge was filed Tuesday against 24-year-old Cristhian Rivera, an undocumented immigrant, sparking a renewed debate over immigration status.

Tibbetts, a 20-year-old rising sophomore at the University of Iowa, disappeared the evening of July 18 while jogging in the rural farming town of Brooklyn, a close-knit community of about 1,500 residents.

The college student's body was found in a farm field on Tuesday.

"Our hearts are broken," her family said in a statement. "We thank all of those from around the world who have sent their thoughts and prayers for our girl. We know that many of you will join us as we continue to carry Mollie in our hearts forever."

Rivera worked for four years at Yarrabee Farms where he gave his employers a state-issued photo ID and a social security card -- but in a different name, according to Dane Lang of Yarrabee Farms.

"We screen every applicant through the Social Security Administration social security number verification service," Lang said at a news conference Wednesday. "What we learned in the past 24 hours is that our employee is not exactly who he said he was."

Lang said he learned on Wednesday that the Social Security Administration employment verification service that the farm uses is not the same as the government's newer E-Verify system.

"Our family member who handles the verification process believed the systems were the same," Lang explained.

The company plans to enroll and use E-Verify going forward, Lang said.

"He came to work everyday, was on time and got along with his co-workers," Lang added of the suspect.

Defense attorney Allan Richards said in a court document that an employer said Rivera has legal permission to be in the country, The Associated Press reported.

U.S. Citizenship and Immigration Services spokesman Michael Bars told ABC News, "A search of records by USCIS revealed Rivera did not make any DACA requests nor were any grants given. We have found no record in our systems indicating he has any lawful immigration status."

Rivera made an initial court appearance on Wednesday and is due to return to court on Aug. 31. He has not entered a plea. When asked if he had anything to say, Rivera, through an interpreter, said "no."

Bond for Rivera was set at $5 million.

After Tibbetts vanished July 18, and her disappearance turned from days into weeks, federal and state investigators joined the search in the small town.

"Ultimately, what led us to Mr. Rivera was surveillance video from a residence here in the community of Brooklyn," Mortvedt said.

The video was found late last week, Mortvedt said, and "investigators went through the video and it took hours and hours and hours, frame by frame ... and eventually saw Mollie."

The video showed Tibbetts jogging and Rivera's car going by, officials said, and Rivera was tracked down by investigators Monday.

In an interview, Rivera told authorities he saw Tibbetts running, got out of his car and ran alongside of her, Rick Rahn of the Iowa Division of Criminal Investigation said.

Rivera said Tibbetts grabbed her phone and said, "I'm gonna call the police," according to an arrest affidavit.

Rivera told authorities he then panicked, got mad and "blocked" his "memory," and didn't remember anything after that until he reached an intersection, according to the affidavit.

Rivera said he then drove to a field entrance and into a cornfield driveway, before realizing he had Tibbetts in the trunk, the affidavit said.

Rivera said he went to get the young woman out of the trunk and saw blood on the side of her head, according to the affidavit.

Rivera then said he dragged the college student from his car to a secluded part of a cornfield and left her in corn leaves, face-up, the arrest affidavit stated.

Rivera led authorities to Tibbetts' body, according to Rahn.

"A tragic end," Mortvedt told ABC News. "All of us were hoping for a much better outcome for Mollie and her family."

"It's every parent's worst nightmare," family friend Linda Safir told ABC station KGO in San Francisco.

"So sad, so wrong," Safir said. "She had so much to give."

"Mollie was a sweet girl," added Katie Murphy, principal at the Corpus Christi School where Tibbetts was a former student. "The best gift we can give is to be a little like Mollie today."

ABC News' Rachel Katz, Briana Montalvo and Matt Foster contributed to this report.