(CNN) For half a decade, serial killer John Wayne Gacy prowled the streets of Chicago in search of young, vulnerable boys and men to lure back to his Norwood Park home.

Gacy is believed to have murdered at least 33 men between 1972 and 1978. Some 40 years later, six of those men are still unidentified.

But one family was brought closure Wednesday, as Cook County authorities identified James "Jimmie" Byron Haakenson as another victim of the so-called "killer clown."

Police: Victim was murdered shortly after coming to Chicago

Haakenson was 16 years old when he left his home in St. Paul, Minnesota, in search of a different life in a bigger city in 1976, Cook County Sheriff Thomas Dart told reporters Wednesday.

The teenager came to Chicago in early August and called his mom on August 5, 1976, to let her know he had arrived. It would be the last time she would hear from her son.

Police believe Gacy murdered Haakenson shortly after he made that phone call home, quite possibly that same day.

It is not known how Haakenson and Gacy met. Gacy was known for searching areas around Chicago looking for men who were gay, alone or looking for work.

Gacy would lure men to his home on false pretenses, often offering them rides, money, drugs, alcohol or a job. He would then impair them before sexually assaulting, torturing and killing them.

Authorities used DNA to identify victim

By the time police uncovered the crawlspace in Gacy's home in 1978, Haakenson's body was unidentifiable. For 39 years, he was given a new identity: Victim No. 24.

In the 1970s, police could only identify victims using dental records. Cook County officials removed the jawbones from the eight unidentified Gacy victims before burying them in county cemeteries, Dart said.

County officials found the bones did not provide enough information for four of the unidentified victims, and in 2011, authorities exhumed the bodies to gather more DNA.

Dart said authorities gathered enough DNA evidence on the victims and are ready to start bringing closure to their families. Dart said he hopes more families will come forward in the near future so more victims can be identified.

Photos: Infamous serial killers Photos: Infamous serial killers John Wayne Gacy killed 33 men and boys between 1972 and 1978. Many of his victims, mostly drifters and runaways, were buried in a crawlspace beneath his suburban Chicago home. Here's a look at some other notorious convicted serial killers. Hide Caption 1 of 26 Photos: Infamous serial killers Jeffery Dahmer was sentenced to 15 consecutive life terms for the murders of 17 men and boys in the Milwaukee area between 1978 and 1991. Dahmer had sex with the corpses of his victims and kept the body parts of others, some of which he ate. Dahmer and another prison inmate were beaten to death during a work detail in November 1994. Hide Caption 2 of 26 Photos: Infamous serial killers Law enforcement officers meet in San Francisco in 1969 to compare notes on the Zodiac Killer, who is believed to have killed five people in 1968 and 1969. The killer gained notoriety by writing several letters to police boasting of the slayings. He claimed to have killed as many as 37 people and has never been caught. Hide Caption 3 of 26 Photos: Infamous serial killers Authorities said DNA recovered from the body of Mary Sullivan matches that of her suspected killer, the confessed Boston Strangler, Albert DeSalvo. After a sample was secretly collected from a relative, DeSalvo's body was exhumed in July 2013 for more DNA testing. From mid-1962 to early 1964, the Boston Strangler killed at least 13 women. DeSalvo was stabbed to death in 1973 while serving a prison sentence for rape. Hide Caption 4 of 26 Photos: Infamous serial killers Ed Gein killed at least two women and dug up the corpses of several others from a cemetery in Wisconsin, using their skin and body parts to make clothing and household objects in the 1950s. Hide Caption 5 of 26 Photos: Infamous serial killers In 1973, Juan Corona, a California farm laborer, was sentenced to 25 consecutive life sentences for the murders of 25 people found hacked to death in shallow graves. Hide Caption 6 of 26 Photos: Infamous serial killers Joseph Paul Franklin was convicted in 1997 of murdering Gerald Gordon outside a St. Louis synagogue in 1977. Franklin was also convicted of at least five other murders, receiving a string of life sentences, but he suggested that he was responsible for 22 murders. He was best known for shooting Hustler publisher Larry Flynt, who was paralyzed from the attack. Franklin was executed in November 2013. Hide Caption 7 of 26 Photos: Infamous serial killers In 1977, David Berkowitz, also known as Son of Sam, confessed to the murders of six people in New York City. Berkowitz, now serving six consecutive 25-to-life sentences, claimed that a demon spoke to him through a neighbor's dog. Hide Caption 8 of 26 Photos: Infamous serial killers Cousins Kenneth Bianchi, seen here, and Angelo Buono were charged with the murders of nine women between 1977 and 1978. Also known as the Hillside Stranglers, the cousins sexually assaulted and sometimes tortured their victims, leaving their bodies on roadsides in the hills of Southern California. Hide Caption 9 of 26 Photos: Infamous serial killers Wayne Williams killed at least two men between 1979 and 1981, and police believed he might have been responsible for more than 20 other deaths in the Atlanta area. Williams was convicted and sentenced to two life terms in 1982. Hide Caption 10 of 26 Photos: Infamous serial killers After serving 15 years for murdering his mother, Henry Lee Lucas was convicted in 1985 in nine more murders. Lucas was the only inmate spared from execution by Texas Gov. George W. Bush. Hide Caption 11 of 26 Photos: Infamous serial killers Richard Ramirez, also known as the Night Stalker, was convicted of 13 murders and sentenced to death in California in 1989. The self-proclaimed devil worshiper found his victims in quiet neighborhoods and entered their homes through unlocked windows and doors. Hide Caption 12 of 26 Photos: Infamous serial killers During a routine traffic stop, a police officer found a dead U.S. Marine in the front seat of a car driven by Randy Steven Kraft. Kraft was linked to 45 murders and sentenced to death in 1989. He would pick up hitchhikers, give them drugs and alcohol, sexually assault them and then mutilate and strangle them. Hide Caption 13 of 26 Photos: Infamous serial killers Ted Bundy raped and killed at least 16 young women in the early to mid-1970s before he was executed in 1989. A crowd of several hundred gathered outside the prison where he was executed, and they cheered at the news of his death. Hide Caption 14 of 26 Photos: Infamous serial killers Joel David Rifkin was stopped by police for driving without a license plate when a body was found in his pickup. Rifkin killed 17 women in New York between 1991 and 1993 and was sentenced to life in prison. Hide Caption 15 of 26 Photos: Infamous serial killers Charles Ng, seen here, and accomplice Leonard Lake tortured, killed and buried 11 people in northern California between 1984 and 1985. After the men were arrested for shoplifting, police found bullets and a silencer in their car and took them into the police station for questioning. Lake killed himself there with a cyanide pill. Ng was later sentenced to death. Hide Caption 16 of 26 Photos: Infamous serial killers Robert Lee Yates Jr. killed 15 people, most of them between 1996 and 1998. He buried one of them in a flower bed by his house in the Spokane, Washington, area. Most of his victims were prostitutes or drug addicts he killed in his van. He is on Washington's death row. Hide Caption 17 of 26 Photos: Infamous serial killers Gary Leon Ridgway, also known as the Green River Killer, confessed to 48 killings after his DNA was linked to a few of his victims. Remains of his victims, mostly runaways and prostitutes, turned up in ravines, rivers, airports and freeways in the Pacific Northwest. Hide Caption 18 of 26 Photos: Infamous serial killers Aileen Wuornos was executed in Florida in 2002 for the murders of seven men whom she had lured by posing as a prostitute or a distressed traveler. Hide Caption 19 of 26 Photos: Infamous serial killers Derrick Todd Lee was accused of raping and killing six women in Baton Rouge, Louisiana, between 2001 and 2003. He was arrested in Atlanta for the murder of Charlotte Murray Pace, convicted in 2004 and sentenced to death. Hide Caption 20 of 26 Photos: Infamous serial killers Danny Rolling pleaded guilty to the 1990 murders of five students he raped, tortured and mutilated in Gainesville, Florida. Rolling was also found responsible for a 1991 triple homicide in Shreveport, Louisiana, and was executed in 2006. Hide Caption 21 of 26 Photos: Infamous serial killers Angel Maturino Resendez, also known as the Railway Killer, was a drifter from Mexico. During the 1990s, he would rob and kill his victims near railroad tracks on both sides of the border and then hop rail cars to escape. Resendez was executed in 2006. Hide Caption 22 of 26 Photos: Infamous serial killers Pig farmer Robert Pickton was charged with 26 counts of murder after police found the bodies of young women on his farm in Port Coquitlam, British Columbia. He was convicted of six murders in 2007, and he is serving a life sentence. Hide Caption 23 of 26 Photos: Infamous serial killers The BTK Strangler, Dennis Rader, killed 10 people between 1977 and 1991 in the Wichita, Kansas, area. He was sentenced to 10 consecutive life terms in 2005. Rader named himself BTK, short for "bind, torture, kill." Hide Caption 24 of 26 Photos: Infamous serial killers Police found the decomposing and buried bodies of 10 women and the skull of another woman at the Cleveland home of ex-Marine Anthony Sowell. He was convicted and given the death penalty in 2011. Hide Caption 25 of 26 Photos: Infamous serial killers Chester Dewayne Turner was sentenced to death for murdering 14 women and one victim's unborn fetus in the Los Angeles area between 1987 and 1998. Turner was later convicted and sentenced to death for four more murders. Hide Caption 26 of 26

Nephew of victim searched for answers

It was earlier this year when a nephew of Haakenson's reached out to the county to find out more about his uncle.

Dart said the nephew came across information on the county's recent efforts to identify the victims. Shortly after, he persuaded his father and aunt, Haakenson's brother and sister, to take a DNA test.

The DNA submitted by the family members was an "immediate hit" on Victim No. 24, Dart said, which quickly led to identifying Haakenson.

It wasn't the first time family members came forward to link Haakenson's disappearance to John Wayne Gacy.

Haakenson's mother went to authorities in 1979 to see if her son was a victim, Dart said. But due to limited resources at the time and the mother's lack of dental records, nothing was recovered. The mother passed away in the early 2000s, Dart said.

Timeline of murder determined from positions of victims

Cook County authorities used other victims' positions in the crawlspace of Gacy's suburban Chicago home to narrow the timeframe of Haakenson's death.

Haakenson's body was found between the bodies of two other men: Rick Johnston and another unidentified boy, referred to by police as Victim No. 26.

Johnston, whose body was found on top of Haakenson's, is believed to have been murdered by Gacy on August 6, 1976, after attending a concert at the Aragon Ballroom in Chicago.

Dart said authorities believe the third victim, whose body was found below Haakenson's, was murdered in July or August of 1976.

Police urge people to come forward

When remains were first uncovered in Gacy's home in 1978, eight victims were unidentified. But due to advancements in technology, that number has been reduced to six.

Dart said the victims were identified because "people agreed to come forward with DNA."

Authorities are now urging people who had loved ones who went missing in Chicago during that period to come forward and submit their DNA -- and hopefully get some answers.

"Every family deserves closure, without hesitation," Dart said.