Whiskers of a 121-year-old mustache came into view of the Penn Museum archaeologists once they finally reached 10 feet deep.

Then, stunningly, the dead man’s tie could be seen amid the soupy ooze of the coffin. Outlines of a suit somehow survived being buried for more than a century.

The mystery surrounding who wore that suit into the grave has remained as resilient with the passage of time — and despite the overwhelming evidence those Penn scientists have gathered in the last few months.

It is H.H. Holmes, if the DNA evidence pulled from the remains is to be believed, lead archaeologist Samantha Cox said.

For the first time, Cox and her team shared photographs from inside the grave and throughout the exhuming process. The pictures provide a fascinating look at what happens to a body after 120 years underground, and are the first glimpses of what remains of the man often described as America's first serial killer.

[NATL] Photos From the Grave of 'America's First Serial Killer'

Holmes reputedly killed dozens at the “Murder Castle Hotel” in Chicago. He built the hotel equipped with secret rooms, chambers and a spot for dissections in the basement. With visitors from around the globe visiting the city’s World’s Fair in 1893, Holmes’ unwitting guests checked in but some never left.

He was eventually imprisoned at Moyamensing Prison in South Philadelphia, put on trial, and hanged in 1896 for his mass murder spree. Or so the news reports at the time say.

The legend of Holmes is a different story. His great-great-grandson, Jeff Mudgett, has long believed that his ancestor, whose real name was Herman Mudgett, faked his death and escaped the hangman’s noose.

Mudgett’s search for truth led to an eight-part television series this summer on the History Channel. As part of that show, Cox and her team led the exhumation of Holmes’ grave site at Holy Cross Cemetery in Delaware County.

NBC10 Investigators were first to unearth the growing mystery in April of the Holmes conspiracy that he escaped death. Then, in July, NBC10 exclusively reported that a search for the truth was underway — with Holy Cross Cemetery in Delaware County as the epicenter. Over the following months, fascinating findings emerged about the fate of Holmes.

H.H. Holmes is considered the United State’s first serial killer. Known mostly for his “Murder Castle” in Chicago, Holmes was actually caught and jailed in Philadelphia. He was ultimately executed, but the man’s family are calling that fact into question. NBC10 Investigator George Spencer digs into the case that has captured the attention of crime and mystery lovers the world...

The DNA evidence was sent to a laboratory at King’s College in London, England. Analysts there compared remains from the skull in the grave to DNA from Jeff Mudgett.

“The best that they can tell us is that the DNA is related, is a person who is related, to the living Mudgett,” Cox said.

In addition to the genetic testing, investigative research by Cox and her team found that medical records from the late 1800s matched up the serial killer with the remains in the grave.

“From a scientific standpoint, to us, there’s no doubt,” Cox said.

The archaeologists documented their dig in numerous photographs that they shared with NBC10. Those pictures show surprises along the way even beyond the incredibly preserved remains: a partially hardened layer of concrete requested by Holmes; an empty coffin; a wooden placard with an etching that read “H H Holmes.”

Finally, there were the skeletal and oozy remains 10 feet down.

The History Channel’s “American Ripper” series, which starred Mudgett, also chronicled the dig and the resulting tests that ultimately concluded Holmes hanged and was buried at Holy Cross.

Mudgett, however, isn’t convinced. He wants another DNA test done.

“The lab had a bias, which in a court of law, would result in the evidence being excluded,” Mudgett said.

The head of DNA analysis at King’s College, Professor Denise Syndercombe Court, said in a statement to NBC10 that bias has nothing to do with sample-testing.

Here is the full statement from Court:

"We are an accredited laboratory that follows ISO17025 guidelines. Analysed profiles are provided electronically from the molecular analyser and are produced independently by different analysts. No personal identifiers are given to the samples, only unique numbers, so analysts will not be aware of what samples are being run. Although the person reporting the results would be aware of the source of the material and indeed would have selected the appropriate analytical technique in order to answer the question at issue, their interpretation will only be based on the output from the analyser. As professional forensic geneticists they are used to dealing with forensic evidence and presenting the results of the analysis in an objective and unbiased way.”

A South Jersey family is revealing their unexpected connection to a notorious serial killer with ties to Philadelphia. After watching NBC10’s earlier report on serial killer H.H. Holmes, they decided to reveal a handwritten note they claim was signed by Holmes that they found in their family Bible. NBC10 investigative reporter George Spencer has the preview for tonight’s story on...