WASHINGTON — Reps. Beto O’Rourke of El Paso and Joaquin Castro of San Antonio are among several Texas Democrats calling for a deeper Customs and Border Protection investigation into Juan David Ortiz, a longtime Border Patrol agent accused of killing four women this month in and around Laredo.

Ortiz, 35, had worked for CBP for 10 years, most recently as an intelligence supervisor. In a letter to CBP Commissioner Kevin McAleenan, the congressmen asked CBP to determine if Ortiz was acting in his official capacity during the slayings, if he used government equipment or databases to carry out the crimes, and if the department missed potential warning signs.

"Like you, our priority is to provide for the well-being and safety of the populations we serve. To do so, we must learn from any mistakes made in this case," the letter says.

Entrusted with the role of overseeing @DHSgov, we need to know whether Juan David Ortiz was acting in his capacity as a Border Patrol agent at any time during the alleged crimes. https://t.co/zEzhsnG9Cl (1/3) pic.twitter.com/CpAc8F2P8v — Joaquin Castro (@JoaquinCastrotx) September 20, 2018

Reps. Eddie Bernice Johnson of Dallas and Al Green and Gene Green, both of Houston, were also among the 18 lawmakers who signed the letter.

A spokesman for O’Rourke declined to comment further on the letter. A spokeswoman with CBP said the agency would respond to the lawmakers directly.

Rep. Henry Cuellar, a Democrat who represents the Laredo area where the murders occurred, did not sign the letter. Cuellar did, however, express concern to a CNN affiliate station that Ortiz might have used his supervisory role to keep track of developments in murder investigations. He talked to McAleenan about improving vetting for Border Patrol agents.

Ortiz confessed to killing four women and kidnapping a fifth after he was arrested Sept. 15. He has been charged with four counts of murder and one count of aggravated kidnapping.

Authorities said Ortiz was on suicide watch as of Wednesday. He has been placed on unpaid, indefinite suspension from CBP, a Border Patrol official told reporters.

O’Rourke is combating attacks that he is too soft on immigration policy, including an ad released Tuesday by Ted Cruz that accuses O’Rourke of wanting to “decriminalize unauthorized border crossings.”

"Senator Cruz has released another factually incorrect attack ad," O'Rourke spokesman Chris Evans said.

Evans said O’Rourke was advocating for not criminally prosecuting asylum seekers who present themselves between ports of entry.

This weekend, O’Rourke will head to the Rio Grande Valley for campaign events with Castro and his brother Julián, who served as the mayor of San Antonio from 2009 to 2014 and then joined former President Barack Obama’s cabinet as the secretary of Housing and Urban Development.