A key lawmaker who exposed a troubling federal turf battle in the immediate aftermath of December’s San Bernardino terror attack charged Wednesday that government officials are following a familiar pattern by hunting down the whistleblowers behind the disclosure.

Sen. Ron Johnson, R-Wisc., said he learned his sources are being sought by Immigration and Customs Enforcement immediately following a dramatic hearing Tuesday in which ICE and U.S. Citizenship and Immigration Services officials acknowledged the disturbing incident on Dec. 3, one day after a terrorist couple gunned down 14 at a county office party.

“I am concerned that ICE is attempting to identify and retaliate against whistleblowers who revealed a lack of cooperation between USCIS and ICE in the aftermath of the terror attacks in San Bernardino,” Johnson said in a follow-up hearing Wednesday. “Those who have the courage to come forward should not be retaliated against.”

“I am concerned that ICE is attempting to identify and retaliate against whistleblowers who revealed a lack of cooperation between USCIS and ICE in the aftermath of the terror attacks in San Bernardino.”

- Sen. Ron JOhnson, R- Wisc.

Johnson further expressed his concerns about retaliation in a letter to Department of Homeland Security Secretary Jeh Johnson and DHS Inspector General John Roth.

Johnson did not identify the person or persons who told him that USCIS bureaucrats barred federal investigators from their building when they came to interview Enrique Marquez a day after the terror attack. Marquez was a close friend of Syed Farook, who, with his wife Tashfeen Malik, carried out the bloody rampage.  Marquez was later charged with supplying the couple assault rifles used in the attack, as well as other crimes.

 Marsha Catron, Department of Homeland Security Investigations spokesperson, told FoxNews.com, “DHS will respond directly to the Senator.

"DHS does not tolerate retaliation against employees who bring possible misconduct to light and complies with all whistleblower protection laws. As public servants working for both law enforcement and non-law enforcement components, our employees are held to the highest standard of professional and ethical conduct."

At the Tuesday hearing where Johnson, chairman of the Senate Homeland Security and Governmental Affairs Committee, first raised the issue, ICE Director Sarah Saldana and USCIS Director Leon Rodriguez blamed poor communication for the fact that a federal agency impeded an investigation into a terror attack that had left 14 dead and 22 injured a day earlier.

“How can you explain that they would not let Homeland Security agents in the building when they are saying, ‘Listen you could have a potential terrorist here involved in what just happened yesterday in the slaughter of 14 Americans?’” Johnson thundered. “And they don’t even allow them in the office? How could that have possibly happened?”

Instead of trying to improve communications, Johnson said, it appears ICE and its parent agency, DHS, are trying to root out his source. Johnson believes the whistleblowers could face retribution for the revelation.

"The federal government has a very poor record of retaliation,” Johnson said. “We’ve held numerous hearings about this. It is really quite shocking how often the federal government retaliates. But I certainly will not stand for it, and I certainly don’t think this committee will stand for any retribution against those who had the courage to come forward to reveal this incident."

Federal law expressly protects federal employees who provide information to Congress.

In the Dec. 3 incident, USCIS agents were investigating Marquez for marriage fraud, stemming from his 2014 union with Mariya Chernykh, a Russian national married to Farook’s brother.

Rodriguez told Johnson’s committee that it was a mistake for his agency’s San Bernardino office to refuse entry to ICE investigators.

“The guidance was to facilitate what Homeland Security Investigations was trying to accomplish,” he said. “Unfortunately, it all happened so quickly that it was incorrectly perceived that our folks were trying to obstruct what ICE was trying to do. There was never an actual intent to prevent them from doing what they needed to do.”

Saldana testified she was initially concerned when her agents were blocked, but told lawmakers there was “confusion” and “chaos” in San Bernardino the day after the attack.

“We had immediate conversations when it came to my attention,” Saldana said. “It was taken care of and clarified immediately. We did get the information we needed.”

Both Farook and Malik were killed by law enforcement after their morning attack. Marquez is accused of making false statements in connection with his weapons purchases used in the San Bernardino shooting. Prosecutors also have alleged that Marquez and Farook plotted in 2011 and 2012 to carry out attacks at Riverside City College and on the 91 Freeway.

Marquez, who has pleaded not guilty, faces up to 50 years in prison if convicted.

Johnson’s committee is already investigating another case of retaliation inside DHS. Homeland Security Investigations Agent Taylor Johnson testified last year about retaliation against her and other whistleblowers who raised concerns about foreigners from countries with terror ties getting green cards under the DHS’s E-B5 Visa Program. She testified that high-ranking USCIS officials and operatives of Senate Minority Leader Harry Reid threatened her and her team.

Taylor Johnson was fired last month, as part of a possible pattern, according to the senator. She has mounted a fund-raising effort to pay her legal fees.

“ICE has a track record of retaliating against whistleblowers, as in the case of Homeland Security Investigations Agent Taylor,” Johnson said.