Chairman of the Joint Chiefs of Staff Gen. Mark Milley told lawmakers on Thursday that there “were probably some missed signals” leading up to the alleged murder of Army Spc. Vanessa Guillén.

“I suspect, though I don't know, that there were probably some missed signals,” Milley told the House Armed Services Committee. “And one of the key lessons that we've learned in other situations is that when we do get early warning, to take action, and take action swiftly and appropriately. 

“So … my guess is that will probably come out in this case, and that will be one of the things that we need to implement for the future to make sure it doesn't happen again,” he added.

Milley addressed Guillén's case alongside Defense Secretary Mark Esper, who called the situation “tragic.” 

Since investigators determined that Guillén was allegedly murdered at Fort Hood in her unit's armory room, lawmakers have demanded answers while some have asked other government agencies to investigate the Army's handling of the investigation its sexual assault prevention and response program. 

Related: Remains of Vanessa Guillen positively identified, family attorney says

While Army investigators have said they don't yet have evidence that Guillén was sexually harassed, the 20-year-old soldier's family said that she told them she was targeted by a superior at Fort Hood

“We’ve got to continue to work at what is believed to be … the underlying issue, and that was she was sexually harassed, if not assaulted, by the soldier in question,” Esper said on Thursday. “That is something that continues to be a stain on the profession.” 

Though “a lot of progress” has been made in the military to combat sexual assault and harassment, Esper said, there's still work left to do. 

“We need to get to zero tolerance of sexual harassment and sexual assault, and we need to make sure that everybody in our ranks knows where they can go to for help, where they can find help,” Esper said. 

“So that is my commitment, and I know that's the Chairman's commitment as well.”