Sen. Mitt Romney (R-UT) on Tuesday expressed support for President Donald Trump’s call to assist Mexico with combating drug cartels operating along the U.S.-Mexico border following the murder of nine Americans in the border state of Sonora.

Speaking to reporters on Capitol Hill, Romney urged the Mexican government to “go after” the cartel gunmen behind the ambush attack on nine relatives who belong to the LeBaron family, a Mormon community long settled in northern Mexico.

“It’s moms and children. This is really unthinkable. And I agree with the president when he says that Mexico needs to really knuckle down and go after these cartels, and stop this escalating levels of violence,” said the Utah Republican.

“And [I do] hope that if there’s a way we can help in that effort, that we are called upon to do so,” he added.

Romney backs Trump's call to cooperate with Mexico to fight cartels pic.twitter.com/qSJMIEE2Ne — Reuters (@Reuters) November 5, 2019

Earlier Tuesday, Romney, a prominent member of The Church of Jesus Christ of Latter-day Saints, expressed his condolences in the wake of the attack and called for the U.S. and Mexico to hold the suspects “accountable.”

Romney wrote on Twitter:

Ann and I are heartbroken for the victims of the horrific attacks in Mexico. Our prayers are with their families who have suffered such an unspeakable tragedy. The U.S. must work with Mexican officials to hold accountable those responsible for this senseless violence.

Ann and I are heartbroken for the victims of the horrific attacks in Mexico. Our prayers are with their families who have suffered such an unspeakable tragedy. The U.S. must work with Mexican officials to hold accountable those responsible for this senseless violence. — Mitt Romney (@MittRomney) November 5, 2019

Drug cartel gunmen ambushed three SUVs along a dirt road, slaughtering six children and three women — all U.S. citizens living in northern Mexico — in a grisly attack that left one vehicle a burned-out, bullet-riddled hulk, authorities said Tuesday.

The dead included 8-month-old twins. Eight youngsters were found alive after escaping from the vehicles and hiding in the brush, but at least five had gunshot wounds or other injuries and were taken to the U.S. for treatment, officials said.

One woman was killed after she apparently jumped out of her vehicle and waved her hands to show she wasn’t a threat, according to family members and prosecutors.

Mexican Security Secretary Alfonso Durazo said the gunmen may have mistaken the group’s large SUVs for those of rival gangs.

President Donald Trump reacted furiously to the ambush and pledged to help assist Mexico with fighting drug cartels.

….monsters, the United States stands ready, willing & able to get involved and do the job quickly and effectively. The great new President of Mexico has made this a big issue, but the cartels have become so large and powerful that you sometimes need an army to defeat an army! — Donald J. Trump (@realDonaldTrump) November 5, 2019

This is the time for Mexico, with the help of the United States, to wage WAR on the drug cartels and wipe them off the face of the earth. We merely await a call from your great new president! — Donald J. Trump (@realDonaldTrump) November 5, 2019

“This is the time for Mexico, with the help of the United States, to wage WAR on the drug cartels and wipe them off the face of the earth. We merely await a call from your great new president!” he tweeted.

The AP contributed to this report.