Morgan Harrington, left, and Hannah Graham. (Courtesy of Harrington family; Charlottesville Police Department via the Associated Press)

ON THE night that University of Virginia student Hannah Graham disappeared, two people saw her with the man later convicted of killing her. Both noticed something amiss. “He’s gonna [expletive] her up,” one witness said of Ms. Graham’s murderer; he “did not look friendly” was the assessment of another. Neither took action, which should prompt questions — not to cast blame, but to focus attention on the need to educate and empower bystanders to intervene.

New details about the circumstances surrounding Ms. Graham’s murder were revealed in court documents that accompanied the conviction and sentencing of Jesse L. Matthew Jr. In retrospect, it seems obvious that someone should have done something that Friday night in September 2014 when Ms. Graham, 18, disappeared from Charlottesville’s Downtown Mall. Likewise, people who passed by 20-year-old Morgan Harrington, another victim of Mr. Matthew, the night of Oct. 17, 2009, as she stood alone and obviously intoxicated trying to thumb a ride from a concert, probably wish they had acted differently. Law enforcement officials as well as advocates for sexual assault victims pointed to the natural tendency not to get involved; “human inertia” was the label used by one official involved in the Virginia cases.

It’s important, according to those involved in bystander intervention programs, to acknowledge that asking people to step up and do something when they see a problematic or questionable situation can be difficult. Is this really an emergency? If it’s not, won’t I be embarrassed? Why aren’t others taking action? And then there can be uncertainty about what specific action to take.

So it’s good that the community shaken by the deaths of these two young women has taken steps to try to prevent future tragedies. The parents of Ms. Harrington founded Help Save the Next Girl, while the University of Virginia developed several initiatives to increase awareness of bystander intervention tactics. U-Va. students have started a campaign to involve downtown merchants in spreading the word about the importance of early bystander intervention. More people are enrolling in training programs that provide specific guidance on actions.

And then there is the advice being sounded by the authorities who brought Mr. Matthew to justice: If in doubt, call police to check it out.