Travelers had arrived at an airport in Kentucky, preparing to board an American Airlines flight bound for North Carolina.

But witnesses told Fox affiliate WDRB the scene at the gate seemed “tense.”

“You could tell the employees knew something was going on,” Frances Wise told the station.

Soon, passengers found out why: The pilot had been arrested.

Passengers told WDRB they thought it was for something like drinking alcohol on the job. In fact, Christian Richard Martin, a pilot for American Airlines subsidiary PSA Airlines, had been arrested in cold-case triple homicide that had occurred three years earlier in a small town in Kentucky.

Kentucky Attorney General Andy Beshear announced Saturday that Martin was indicted on charges of murder in the deaths of Calvin and Pamela Phillips and Edward Dansereau, who were discovered dead in 2015 in Pembroke, near the Tennessee border. Martin was arrested early Saturday morning at Louisville International Airport on three counts of murder, as well as counts of arson, burglary and tampering with physical evidence, the authorities said.

“There will be many steps from here,” Beshear said in a video statement. But, the state attorney general added, the indictment illustrates what can result “when you never stop seeking justice, when you never give up on a case.”

American Airlines said in a statement it was “deeply saddened” to learn about the allegations against Martin, who has been a pilot for PSA Airlines since January 2018. The airline said he underwent a background check and “recurrent vetting” but that there was no “criminal history that would disqualify him from being a commercial pilot.”

After the indictment, American Airlines said Martin has been placed on administrative suspension pending the outcome.

“We have an unwavering commitment to the safety and security of our customers and team members, and we will provide any investigative assistance possible to law enforcement throughout their investigation,” the statement said.

It is not yet clear whether Martin has an attorney in the case.

In November 2015, Calvin Phillips was discovered dead in the cellar of his home from an apparent gunshot wound, authorities said. His wife, Pamela, and a neighbor, Dansereau, were found dead in a nearby field inside Pamela’s car, which had been burned, according to the Associated Press.

NBC affiliate WSMV reported Martin had served in the military and was court-martialed in 2015 in a case involving physical and sexual abuse, and mishandling classified information.

Calvin Phillips was listed a potential witness in that case, according to the station.

In fact, Phillips’ son, Matt, told CNN on Sunday that his father had been planning to testify in military court when he was killed.

“I will say that Martin was dishonorably discharged,” Phillips’ son told CNN. “He’s in my view not a military veteran. He was shamefully kicked out of the military. My father had a lot to do with that. And I think we should all be thankful for that, frankly.”

Martin was found guilty of court-martial in May 2016 of two counts of mishandling classified information and of assault on a child under the age of 16, said Army Lt. Col. Emanuel Ortizcruz, a service spokesman. Martin was dismissed from the service, reprimanded, and sentenced to 90 days of confinement, Ortizcruz said.

Martin first joined the military in the Army Reserve in April 1986, shifting between service in the Army National Guard and on active duty through August 2016 as a cavalry scout.

According to local news reports, Martin was listed as a person of interest after the three were killed. But in a 2016 interview with WSMV, Martin denied any involvement in the killings.

“I don’t know why anybody would want to do something to them,” Martin said.

The victims’ families said in a joint statement that the victims were “brutally extinguished — beyond recognition from family.”

“Every day, we are haunted by what was done to them and haunted further that someone was still free to do as they wish, beyond the civility of mankind or laws of our nation,” they said in the statement, which was released Saturday by the state attorney general’s office. “We are overwhelmed with this positive step towards resolution for people we love dearly; Cal and Pam Phillips and Ed Dansereau, and the hundreds of friends, family, neighbors, co-workers and others deeply affected by their brutal end.

“We look forward to justice in court, and we look forward to a verdict to bring an end to this terror, and a fresh start at healing.”

Beshear said he agreed to appoint a special prosecutor to the case a couple year ago when Matt Phillips told him that he was concerned that the murder investigation was not moving forward. Beshear said he assured the family members that “we’re going to do everything we can to help you.”

In the airport Saturday morning, the mood was tense and passengers who were waiting to board their plane were confused.

Wise’s daughter, Ashley Martin (who is no relation to the suspect), called it “startling.” “It’s scary to think this happened so long ago, and they’re just now getting around to catching the guy,” she told WDRB.

“I was definitely stressed,” she added. “I felt like it was a little chaotic and unorganized. The workers .?.?. you could tell they were stressed. You could feel that energy. You could feel the tension from flight attendants.”

Martin, who lives in North Carolina, is being held without bond at the Christian County Detention Center in Kentucky, where he is awaiting trial. He is due in court May 22.