The National Center for Missing & Exploited Children (NCMEC) released new facial reconstruction images on Monday in hopes of identifying two of notorious serial killer John Wayne Gacy’s unknown victims.

Gacy is infamously known for murdering and raping young boys and men between 1972 and 1978 in Cook County, Illinois. He was convicted of murdering at least 33 boys and men in 1978 after police raided his home and discovered several bodies in makeshift graves hidden inside of a crawl space. He was executed by lethal injection at Stateville Correctional Center on May 10, 1994.

Six of the prolific killer’s victims remain unidentified. NCMEC, along with the Cook County Sheriff’s Office collaborated to create new facial reconstructions for two of them, referring to them as John Doe #10 and John Doe #13.

Authorities believe Gacy hunted down his victims as they were hitchhiking and at bus stops, many of whom were travelers, then murdered them in cold blood, according to NCMEC. It’s believed that the serial killer, who was once well-liked and often dressed up as a clown for children in the community, lured the boys and men by posing as a police officer or offering them construction work.

Investigators describe John Doe #10 as being a white male between the ages of 17 and 21 years old. He was between 5-feet-7 inches tall and 5-feet-11 inches tall with unknown hair or eye color, and dental fillings. It is noted that the victim suffered an injury to his left clavicle before his death.

John Doe #13 is believed to be a white man between the ages of 18 and 22 years old. He was between 5-feet-7 inches tall and 6-feet-2 inches tall with wavy, dark brown hair.

Anyone with information about the identify of the unidentified males are urged to contact NCMEC at 1-800-THE-LOST or 1-800-843-5678, or the Cook County Sheriff’s Office at 708-865-6244.

[Feature Photo: Unidentified victims/ NCMEC]