The arrest of a 24-year-old illegal immigrant in the murder of University of Iowa student Mollie Tibbetts sparked both mournful — and fiery — responses from politicians on Tuesday, as they pleaded with Congress to do more to protect U.S. citizens.

Investigators identified Tibbetts' suspected killer as Cristhian Bahena Rivera, an illegal immigrant from Mexico who is believed to have been living in the area around Brooklyn, Iowa, for four to seven years.

President Trump, while in West Virginia speaking at a rally, said Tibbetts' murder "should have never happened."

"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 asked. "Should have never happened. Illegally in our country."

Vice President Mike Pence said he was "heartbroken" by the news of Tibbetts' brutal slaying and offered prayers for the young woman's family and close friends "in this time of unimaginable grief." Pence called for "justice" after police announced Rivera's arrest.

"We commend the swift action by local, state, & federal investigators working in Iowa in apprehending an illegal immigrant, who’s now charged with first-degree murder. Now, justice will be served. We will never forget Mollie Tibbetts," Pence continued in a tweet.

Iowa Gov. Kim Reynolds said she expressed condolences to Tibbetts' family earlier Tuesday, declaring "justice had just begun" after the arrest of Rivera.

"As Iowans, we are heartbroken, and we are angry. We are angry that a broken immigration system allowed a predator like this to live in our community, and we will do all we can bring justice to Mollie’s killer," Reynolds, a Republican, added in a tweet.

"My heart hurts for Mollie’s family. Prayers. 💗," U.S. Ambassador to the United Nations Nikki Haley tweeted after Tibbetts' dad, Rob, confirmed the student's body had been found.

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Fred Hubbell, a Democratic nominee for Iowa governor, tweeted that the news was "truly heartbreaking," adding that "words today will be of little comfort" to Tibbetts' loved ones.

"This is truly heartbreaking. For Mollie’s parents, her family and friends, any words today will be of little comfort," he tweeted. "As a parent and grandparent, your worst nightmare is losing your child."

He went on to praise authorities for their "around the clock" dedication to the investigation.

John Cox, a GOP candidate in California's race for governor, released a statement comparing Tibbetts' murder to the "heartbreaking death" of Kate Steinle, who was shot and killed on a San Francisco pier in 2015. Investigators said the suspect, Jose Ines Garcia Zarate, was in the U.S. illegally. A jury acquitted him of murder, manslaughter and assault last year but convicted him of being a felon in possession of a firearm.

"As a father of four daughters, it crushes my heart to see yet another family go through this nightmare," Cox said. "Those who want to abolish ICE need to consider the consequences of their rash proposal."

He continued, "The Mollie Tibbetts case is one more tragic example of a senseless loss that never should have happened, similar to Kate Steinle’s heartbreaking death in San Francisco."

Texas Governor Greg Abbott pivoted to turn Tibbetts' death into a poltical discussion, partially placing blame on sanctuary cities, though Iowa — where the 20-year-old's body was found in a field covered with corn stalks — doesn't have any designated sanctuary cities.

"An undocumented immigrant is charged for murder of Mollie Tibbetts, the Iowa college student who went missing on July 18," Abbott, a Republican, tweeted. "This is why so many Americans are angry about sanctuary cities. It’s why Texas banned sanctuary cities."

House Majority Whip Steve Scalise, R-La., also called on members of Congress, specifically Democrats, to help push forward stricter immigration legistlation.

MOLLIE TIBBETTS MURDER SUSPECT ID'D AS CRISTHIAN RIVERA, 24, LIVING IN US ILLECALLY

"What will it take for Democrats to renounce their dangerous open borders policies and start to put American citizens first?" Scalise asked. "It’s time they stop blocking common sense bills to restore the rule of law in this country before we see another senseless tragedy like this."

In a nod to recent comments from fellow Republicans, Arizona Rep. Paul Gosar called on Congress to help secure the border.

"Securing our border is about protecting our communities, families and children from dangerous criminal activity and violence that threatens their safety. #SecureOurBorder," Gosar wrote, in part.

Iowa Rep. Steve King also asked for justice to be served.

"Mollie Tibbetts, our hearts are broken. We all prayed for your safe return. May you now be with the Lord and your family one day find a peace," he added.

Fox News' Elizabeth Zwirz, Lee Ross and Samuel Chamberlain contributed to this report.