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Fifty years ago a stranger with a pockmarked face and a “Born To Raise Hell” tattoo on his left arm barged into a Chicago townhouse where a group of student nurses were living and proceeded to lead them “like lambs to the slaughter.”

The intruder’s name was Richard Speck and for five hours he systematically tortured and murdered eight women, raping at least one of them.

So consumed was Speck by his bloodlust that he failed to notice that a ninth student nurse, Corazon Amurao, whom he had briefly taken hostage, had hid under a bunk bed.

When it was over and Speck was gone, the 23-year-old survivor climbed out on a window ledge and screamed for help. She later provided police with a description of the blank-faced intruder who had slaughtered her housemates.

For two days Chicago was gripped by fear amid a massive manhunt to find the man before he could kill again. It ended when Speck was taken from a fleabag hotel to Cook County Hospital after a failed suicide attempt and the attending physician spotted his tattoo.

The crime horrified Chicago and the rest of the country because it was so unfathomable — a massacre for no apparent reason by a remorseless stranger against a group of young women he didn’t know.

And it introduced a term to the American public that has since then become all too familiar: random mass murder.

“It really was the first random mass murder of the 20th century,” William Martin, the assistant Cook County district attorney who prosecuted Speck, told NBC News last week, approaching the 50th anniversary of Speck’s 4½-hour rampage on July 13-14, 1966. “It really was the end of an age of innocence. It changed everything. We all became much more conscious of our security. Eight nurses could be slaughtered in their beds for no reason by a stranger.”

William Martin, a former Assistant State's Attorney and the Chief Prosecutor of mass murderer Richard Speck, poses for a portrait in his office in Oak Park, Illinois, on July 7. Martin holds the book The Crime of the Century, which he co-authored with journalist Dennis L. Breo. Alyssa Schukar / for NBC News

John Schmale, a retired physician whose sister, Nina, was one of the murdered student nurses, also speaks of innocence lost when he recalls that night.

“This was not gang-related like most of the violent crime in Chicago today,” said Schmale, 78, who has set up a Facebook page honoring the memory of his sister and the other victims. “These were girls within six weeks of graduating, members of a respected profession. They were basically kids, girls doing girlie things. This was innocence.”

During his trial, Speck shed no tears for the victims.

“He was totally without contrition, he was totally without remorse,” said Martin, 79, whose 1993 book with Dennis Breo about the massacre, “The Crime of the Century,” has been updated and republished to mark the grim anniversary. “He had no redeeming characteristic whatsoever.”

His icy demeanor also helped fuel a national fascination with the case.

“Knowing what he did, everybody found him creepy,” Martin said. “Speck just stared. Not a thousand mile look into space, but kind of nonreactive. … (He) just sat still and was expressionless.”

Martin said Amurao’s courage on the stand, pointing out the defendant in front of the jury, and her precise recounting of the horrors at 2319 E. 100th St., were key in convicting Speck, though he also left fingerprints all around the townhouse.

From a personal standpoint, Martin said she also helped restore his faith in humanity.

Despite what she witnessed, Amurao, now 73 and living in the Washington, D.C., area, is a “very happy person who enjoys life and laughs a lot.”

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“She still has nightmares about Speck,” Martin said. “She personifies the triumph of good over evil.”

Corazon Amurao, star witness for the prosecution in the trial of Richard Speck, and her mother, Macaria Amurao, leave the courthouse for lunch in Peoria, Illinois, on April 6, 1967. Charles Harrity / AP

Amurao’s nightmares were born on an unusually cool summer night that followed a stormy day. Speck chose for his killing ground a modest, two-story townhouse that the now-defunct South Chicago Community Hospital was using to house their student nurses. It was located in Jeffrey Manor, a middle-class neighborhood in the shadow on the steel mills lining the lakefront.

Armed with a hunting knife and a .22-caliber pistol, Speck broke in through a window around 11 p.m. on July 13, 1966 and made his way upstairs to where the three bedrooms were located. The first door he knocked on belonged to Amurao, one of three Filipino students who lived there, and her roommate.

“In low tones, the man ordered the two students into the adjoining bedroom where the four other nurses were awakened,” according to an account by Chicago Tribune reporter Robert Wiedrich published nine days after the crime was reported. “Then all six were herded into a rear bedroom.”

“Maybe if we were calm and quiet he will be, too. He has been talking to us all and he seems calm enough and that is a good sign.”

In addition to Amurao, there were the two other Filipinas: Merlita Gargullo, 23, and Valentina Pasion, 23; and three Americans: Patricia Matusek, 20, Pamela Wilkening, 20, and the 24-year-old Schmale.

Speck, a 24-year-old ex-con from tiny Kirkwood, Illinois, who spent most of his miserable childhood in Dallas avoiding beatings by his drunken stepfather, sat on the floor and told the women he needed money to get to New Orleans.

Amurao told investigators the American girls did not think Speck would hurt them.

“They told us we more or less had to trust him,” she was quoted as saying in the Tribune article. “Maybe if we were calm and quiet he will be, too. He has been talking to us all and he seems calm enough and that is a good sign.”

Using strips of torn bed sheets, Speck bound the wrists of his captives behind their backs. Then, one after another, Speck walked them out of the bedroom — and to their deaths.

“Like lambs to the slaughter,” was how Wiedrich described it.

It was at this point that Amurao managed to roll under a bed while Speck wasn’t looking. She told police later that none of her friends screamed as they were being led from the room, but she later heard their muffled cries.

From left, top are: student nurses Gloria Jean Davy, 22, Mary Ann Jordan, 20, Suzanne Farris, 21, and Valentina Pasion, 23, and bottom, Patricia Matusek, 20, Merlita Gargullo, 23, Pamela Wilkening, 20, and Nina Schmale, 24, all of whom were slain in 1966 by Richard Speck. AP

When she finally emerged from her hiding place around 6 a.m., several hours after Speck had fled, Amurao found Suzanne Farris, 21, dead in a hallway by the upstairs bathroom from stab wounds to the chest and chin. She later learned that Farris and two other student nurses — Gloria Jean Davy, 22, and Mary Ann Jordan, 20 — had returned to the townhouse in the midst of the killing spree and met the same fate as their housemates.

She found Matusek, Jordan and Wilkening in the east bedroom. Matusek and Wilkening had been strangled. Wilkening, who was sprawled on a bed, had also been stabbed. Jordan was stabbed, in the chest, neck and left eye.

Then Amurao found the bodies of Schmale, Pasion and Gargullo in the west bedroom. There were also knife wounds on the neck of Schmale, who had been gagged with a strip of torn bed sheet and strangled. Pasion had also been strangled. And Gargullo’s throat was slashed.

Downstairs, Davy’s body lay naked on a sofa. She too had been strangled.

Throughout the two-week trial, Speck insisted he was innocent and had no memory of the murders.

But Amurao would not find that out until later because, after finding seven bodies, she climbed out of a second floor window onto the ledge “and began to scream and scream and scream,” Wiedrich wrote.

Speck was found competent to stand trial by a panel of psychiatrists who also diagnosed him as a sociopath. Because of the notoriety, the trial was moved three hours away from Chicago to Peoria and began on April 3, 1967.

Throughout the two-week trial, Speck insisted he was innocent and had no memory of the murders. His public defender Gerald Getty tried in vain to suppress damning evidence against his client.

Speck's defense crumbled when, in a moment of high drama, Amurao walked from witness box to where the accused mass murderer was sitting and with a finger pointed directly at him said, “This is the man.”

Armed with Amurao’s testimony and the fingerprint evidence, it took the jury just 49 minutes on April 15 to find him guilty and recommend the death penalty.

Speck was never strapped into the electric chair. The Supreme Court in 1971 upheld his conviction but reversed the death sentence because potential jurors opposed to capital punishment were excluded from the jury pool.

Instead, Speck was dispatched to the Stateville Correctional Center to serve a 400-year sentence. He died of a heart attack on Dec. 5, 1991. He was 49.

When nobody showed up to claim his body, Speck was cremated and his ashes were scattered at an undisclosed location near Joliet, Illinois.

William Martin, chief prosecuting attorney, is seen after a jury of seven men and five women found Richard Speck guilty of the murder of eight Chicago student nurses on April 15, 1967. Bettmann / Bettmann Archive

Speck regularly refused interview requests. But six years after he died, Martin recounted in his book how Chicago TV reporter named Bill Kurtis got his hands on what would become his sick epitaph.

It was a black and white video filmed behind bars in December 1988, a fake news show starring Speck and his prison lover Ronzelle “Honey Bun” Larimore.

In it, a grotesque-looking Speck sports silk panties and shamelessly shows off ample breasts on a body transformed by smuggled female hormones as he engages in sex with Larimore. At one point, he freely admits to committing the crime that made him infamous, saying he was high at the time but would have “done it sober.”

“Like I always felt,” Speck answers when asked by whoever is filming how he felt after the killings. “Had no feelings. If you’re asking if I felt sorry ... no.”

Asked why he murdered the women, Speck gave a chilling answer that Martin said “sickens me to this day.”

“It just wasn’t their night,” Speck said.