It started with a sketch from memory of a woman Samuel Little says he brutally murdered in 1996. Then Little, a former boxer who has confessed to 93 serial killings over a span of 35 years, just kept drawing pictures of his victims.

On Tuesday, the FBI released 16 of the killer’s drawings of unidentified women in hopes of finding out who they are.

Some of the photos show women with sad eyes with smudged mascara. Details such as his victims’ eye and hair color are eerie. Some look calm. Others look terrified. One is smiling. They are all wearing lipstick.

Until and unless one of his drawings matches a previously unidentified murder victim, it will be impossible to know whether the confessed killer really remembered intricate details like the jewelry and headbands and hairstyles of his victims—or if he just made it up in the quiet of his prison cell.

Investigators say his memory has previously failed him on dates, and they are not yet certain that the details he has drawn are not composites of many women rather than haunting postmortem masterpieces of singular people.

Most of Little’s victims were women living on the edge, either working as prostitutes or barely surviving as drug addicts. Some were transgender women, according to the Los Angeles Times. All of them were strangled and dumped into wooded areas. Most of his victims’ deaths were written off as overdoses or random accidents. Many were never even investigated as homicides.

Little, who was convicted in 2014 of strangling three Los Angeles women between 1987 and 1989, started confessing to these heinous crimes from his prison cell in May of last year. FBI investigators had suspected the 77-year-old might be involved in a number of cold cases they were trying to close, so they started trying to soften him up. Lacking forensic evidence like fingerprints or DNA, they had to elicit a confession.

Eventually, an investigator plied the killer with peanut M&Ms and started talking about a strangulation case in Odessa, Texas, that they were sure he was involved in. That trigger got him talking—and he didn’t quit for days, describing his macabre murders one by one.

He told the investigators shocking details that only a killer would know about the women, cataloguing them in his mind by the cities in which they were committed, according to a chilling account in the Los Angeles Times.

Police eventually corroborated 36 of Little’s confessions to previously unsolved cases. In one case described by the newspaper, his memory was so precise that he could recall the last meal one of his victims ate. The police later verified that it matched the woman’s autopsy results, which listed the contents in her stomach at the time she was killed.

Now the FBI is hoping that his visual memory is as good and that the drawings they released will lead them to the truth about just who Little’s unknown victims are.