Updated

After nearly 10 years and more than 750 leads, law enforcement officials and victims' families remain stumped in one of South Carolina's most heinous killings: A gunman who walked into a motorcycle shop, killed the owner and three employees, and slipped out undetected.

Nov. 6 will mark a decade since the deaths at Superbike Motorsports in Spartanburg County, on a two-lane highway headed from the city toward the Blue Ridge Mountains. Sheriff Chuck Wright has vowed to get the killer off the street, but he now admits he may be waiting for a jailhouse confession.

For the families of the store's owner, service manager, mechanic and bookkeeper, the search for answers is taking a toll. The parents of one victim moved to South Carolina to find justice, but say their hopes that the killer will face justice are fading.

Veteran law enforcement officials say that in recent state history, they can't remember another mass shooting remaining unsolved for so long.

Investigators say all four victims were killed with the same 9 mm pistol. They think the killer came in the back, perhaps through an open garage door, and killed mechanic Chris Sherbert, 26, as he worked. Bookkeeper Beverly Guy, 52, was found just outside the bathroom in the middle of the showroom. Her son, shop owner Scott Ponder, 30, was found just outside the door in the parking lot, and service manager Brian Lucas, 29, in the doorway; officials say they may have been trying to run. They also cite evidence that the killer may have circled back and shot some victims in the head to ensure they were dead. He was a good shot: Officials say he missed his moving targets only a few times.

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Wright says that just before the deaths, Ponder had started a bill of sale for a motorcycle about to be sold. He hadn't written down the customer's name, credit card number or other identifying information.

Investigators won't say whether there were unidentified fingerprints or DNA in the shop -- only that forensic evidence is limited.

"I think this one will be solved in the jailhouse," Wright recently told The Associated Press. "There are very few cold-blooded killers who won't talk."

Wright was elected sheriff in 2004, about a year after the shootings. He said the investigation could have been handled better but wouldn't give specifics, mentioning only that crime scene technicians missed processing an entire room and had to return the next day.

Wright and his investigators are pushing hard a revised sketch of a customer who was in the store less than an hour before the killings. When Wright released the drawing in March 2012, he said he thought that man was the killer. Now Wright says he's not so sure, but he still believes the man has information to crack the case.

Investigators do think the killer was a disgruntled customer. Through the Internet, Ponder sold nationwide. A map in the sheriff's office has pushpins where Ponder's motorcycles were sold. Each pin is somewhere a suspect might live, a place where investigators want to get the word out.

The victims' families have their theories, too. "It runs through my mind constantly," said Lorraine Lucas, the mother of Brian Lucas. "I run that day through my head when I first wake up, and it is the last thing I do at night."

Time has given the families plenty of chances to come up with motives. Some are bizarre, they admit, but with no arrests, they say no one can be sure.

Ponder was searching for his biological father, who disappeared decades ago -- maybe the killer didn't want the shop owner to learn about his dad. Maybe a rival motorcycle owner was angry about Ponder's success and decided to cut out the competition. Maybe the man who discovered the bodies should be looked at -- he saw Ponder and Lucas bleeding just outside the shop and stepped over his dead friends to call 911 from inside the shop even though he had a cellphone.

"We want them to look at every single angle, just not that it was a customer angry at the business," said Tom Lucas, Brian's father.

On Nov. 6, the families will gather in Spartanburg to celebrate their loved ones' lives. One of the speakers will be Scotty Ponder, 9 -- his mother was pregnant with him when father Scott Ponder was killed.

Since the shooting, Melissa Ponder has gone through two divorces. She said she was shattered over losing Scott and is now sorry she has brought men into her life and into that tough situation.

"I used to think, there's no way a crime this big is not going to get solved. But the fact somebody was able to pull the trigger, end four people's lives and go on their way and hasn't felt bad for 10 years, I don't know," she said.

Tom and Lorraine Lucas also feel their hope fading. Tom Lucas said he looks down the road to the 20th anniversary of his son's death and can see himself with a walker, still raising hell.

"How can you get away with a killing like this?" Lorraine Lucas said.

The families say they understand that the sheriff's office is trying to solve the case, and Wright said it keeps him up at night, too. He said he doesn't fault the families for holding on to any theory or version of events.

"But in the end, I need probable cause. I need a case that can go to trial," Wright said.

Terry Guy lost his wife, Beverly Guy, and his stepson. He said he used to dream that deputies would allow him into the killer's cell so he could get his own justice. But over the past 10 years, he's had a change of heart. He fell in love with and married Brian Lucas' sister. Now, Guy said, he just wants to offer the killer forgiveness, and he's sure of only one thing about the investigation.

"I know what I've done, and I know I didn't do it," Guy said. "So who is a suspect? Everyone but me."