To Catch A Killer

Will A Cop's Determination Solve A Mass Murder?

This story originally aired March 3, 2007. It was updated Sept. 6, 2007.

When several family members didn't show up for a birthday party in December, 1997, Phil and Nicoletta Dosso drove to their business to see where everyone was.

As correspondent Harold Dow reports, what they found inside was beyond their comprehension: three of the family members and their long-time friend and partner were all shot execution style. With no forensic evidence, the case would be hard to crack and authorities recruited one very tenacious cop to tackle the case.

Would he be able to track down the killer?

Dec. 3rd was always a special day for Maria Dosso and her husband Frank - it was the date they started dating and on that date in 1997, it was also the tenth birthday of their twin daughters, Mara and Nicole.

The whole family was going to get together for coffee and cake. "I was expecting Frank to get home at around 5:30. At a quarter to six, he wasn't home yet, and no one answered the phone when I called the factory," Maria remembers.

She decided to call her mother-in-law, Nicoletta.

Frank worked for his father, Phil, an Italian immigrant who was co-owner of a thriving manufacturing plant in Bartow, Fla.

Nicoletta and Phil's daughter, Diane Patisso, a young state prosecutor, was supposed to meet her brother Frank and her husband George at the factory. But she was nowhere to be found.

The Dossos decided to drive to the Erie Manufacturing Company to see what had happened. When she walked in, Nicoletta Dosso was devoured by a world of unimaginable horror.

"Diane was on the floor. Oh my God. It was so bad. It was so bad. And I said 'Maybe she's alive. Maybe she's alive,' but she wasn't. She wasn't," she remembers. "And then I said 'Let me go see. Maybe Frankie is…something happened to them, too.'"

Phil Dosso rushed in after his wife, and was also overcome by the carnage. He frantically called 911.

Shot dead were four of the most beloved people in the Dosso's life: not only their daughter, but also their son, their son-in-law, and George Gonsalves, Phil Dosso's longtime business partner and friend.

Gonsalves was usually alone when he closed up the factory, but on that night fate had placed the three others with him. Who would want to kill these four people, placed together by a quirk of timing?

Police believed there was a single killer, one who was very careful: at the crime scene, no fingerprints, DNA or murder weapon were found.

Within two days, the Florida Department of Law Enforcement dispatched Special Agent Tommy Ray, one of its shrewdest homicide detectives, to hunt for a killer who seemed to have ice in his veins

"George Patisso was shot five times in the back of the head, George Gonsalves was shot twice," says Ray, who tells Dow all four victims were shot execution style. "He then comes over where Frank is trying to get up...and then Frank Dosso was shot three times."

Diane Patisso was the last one to be killed. "He chased her out here in the hallway," Ray explains. "Diane was shot twice in the back of the head."

Amid the bloodshed, there seemed to be signs of a robbery. Desk drawers were pulled open, and papers strewn about. But Ray thought it looked staged and two other things caught his eye: dusty shoe prints left on the seat of an office chair and a ceiling tile that was somewhat raised.

Ray checked out more than a thousand leads; all lead back to one man. "The day of the homicide they initially told the Bartow Police that … Nelson Serrano … you know, 'Look at Nelson Serrano,'" Ray explains.

Nelson Serrano was the third partner, along with Dosso and Gonsalves, in two sister companies, Erie Manufacturing and Garment Conveyor Systems.

The businesses had made the three very wealthy men, but bitter fights with Serrano over money began to tear them apart. Dosso and Gonsalves accused Nelson Serrano of graft, then theft, and eventually forced him out.