Rivera is being held on a $1 million cash bond.
Here’s what we know about the 24-year-old man accused of abducting and killing the 20-year-old psychology student, who was last seen going for an evening jog.
1. He might be an undocumented immigrant
Police revealed on Tuesday that Rivera is an undocumented immigrant who has been living in Iowa at least four years, but possibly up to seven. After his arrest, U.S. Immigration and Customs Enforcement lodged a federal immigration detainer, which means he could be deported, the Associated Press reported. Rivera is from Guayabillo, Mexico according to his Facebook page.
Illegal immigration has become a hot-button issue over the past few years, and President Donald Trump wasted no time mentioning Rivera’s status after his arrest. He alluded to Rivera during a rally in West Virginia on Tuesday evening, not long after the announcement that he was in custody.
“You heard about today with the illegal alien coming in, very sadly from Mexico, and you saw what happened to that incredible, beautiful young woman,” Trump said. “It should’ve never happened. Illegally in our country. We’ve had a huge impact, but the laws are so bad, the immigration laws are such a disgrace.”
However, Rivera's lawyer Allen Richards has claimed that his client is not in the U.S. illegally and requested a gag order in the case, the Des Moines Register reported.
"Sad and sorry Trump has weighed in on this matter in national media which will poison the entire possible pool of jury members," Richards wrote in that document.
2. He worked for a Republican politician’s brother
Rivera worked for dairy farm Yarrabee Farms, The Des Moines Register reported. The farm is owned by a prominent Republican family in the area.
In a statement released Tuesday night, farm owner Dane Lang said Rivera was an “employee in good standing" who was vetted through the government's E-Verify system. Lang’s brother is Craig Lang, former president of the Iowa Farm Bureau Federation and a 2018 Republican candidate for state secretary of agriculture.
3. He'd seen her before
"He tells us that he had seen her before but beyond that, I can't tell you anymore," Rick Rahn of the Iowa Division of Criminal Investigation said, according to CBS News. Police said they spotted a Chevy Malibu on surveillance video following Tibbetts the day she vanished, a vehicle that was traced back to Rivera. The Malibu was seen moving back and forth near Tibbetts several times before it started to follow her, according to Rivera's arrest affidavit.
"He tells us that he sees Mollie running. … He actually tells us that he ran alongside of her or behind her," Rahn said. "She took off running. He, in turn, chased her down."
4. He claims he blacked out
According to court documents obtained by CNN, Rivera said Tibbetts threatened to call the cops when he approached her. He claimed he blacked out before coming to at an intersection with Tibbetts' body in the trunk of his car, according to the documents. Rivera said he does remember seeing Tibbetts’ headphones in his lap and taking her bloodied body out of his trunk.
“The defendant further described during the interview that he dragged Tibbetts on foot from his vehicle to a secluded location in a cornfield,” the affidavit says.
“I can’t speak about the motive. I can just tell you that it seemed that he followed her, seemed to be drawn to her on that particular day, for whatever reason he chose to abduct her,” Rahn told reporters at the news conference.
5. He had kept a low profile
Up until this week, Rivera appeared to have kept a low profile. He has been described as someone who kept to himself, according to The Associated Press. He does not appear to have any criminal history.
[Photos: Iowa Division of Criminal Investigation]