CORAL SPRINGS, Florida (CNN) -- Authorities solved a 31-year-old disappearance this year when they found the remains of Jeff Klee, missing since 1977, in a van in a canal.
Jeff Klee had been missing since 1977; his remains were found this year.
But prosecutors have announced that no charges would be filed against the man who, authorities say, admits that he put Klee's body in the van three decades earlier.
"Today is a sad day for our family," Klee's sister, Laurel Steele, told reporters Thursday. "It tests my family's faith to its very core."
Klee's remains were found in March during a routine police sweep for stolen vehicles in the C-14 canal in Coral Springs, Florida. The van was in neutral when police discovered it.
DNA confirmed Klee's identity, but authorities say there was not enough evidence to determine how he died -- and whether he had been killed. Watch Klee's sister react to the decision »
The Broward County State Attorney's Office said the statute of limitations on possible manslaughter charges expired in 1980. As for a more serious charge such as first-degree murder to which a statute of limitations would not apply, prosecutors said they don't have any evidence of premeditation or that the death was caused by a criminal act.
Police had long thought Klee's best friend, David Cusanelli, was the last person to see him alive June 21, 1977.
According to a memorandum released Thursday by the Broward County State Attorney's Office, Cusanelli told authorities this July 28 that he put Klee's body inside his black Chevy van after he was dead and that his brother, Carl Cusanelli, helped shove the van into the canal.
But Cusanelli denied involvement in Klee's death, prosecutors said.
Mitch Polay, the defense attorney for the Cusanelli brothers, reiterated that denial.
He said the brothers' statements "were taken out of context, and they were posed as hypotheticals to drum up potential memories of the event."
"My clients, for 31 years, have denied any involvement," Polay told CNN. "They had no involvement with pushing any van into the water, nor did they have any involvement with the death of Jeff Klee."
According to the prosecution memorandum, Cusanelli told police that he and Klee had an argument over a former girlfriend. Cusanelli said Klee began to chase him out at the canal that night, the document alleges.
Cusanelli said that "all he remembers is, he turned around and saw that Jeff had fallen and was on the ground, and his head was split open, and there was a lot of blood," according to the document.
"There was definitely a confrontation that night, which resulted in Jeff Klee's death," lead Detective David Weissman said Thursday.
Cusanelli told police that he ran away from Klee because he was in fear of his life and that he has no idea how Klee fell. Cusanelli concedes that he may have thrown a rock at Klee, according to the prosecution memo.
Cusanelli, according to the memo, said he panicked and put Klee's body inside his van. He then called his brother Carl, who helped push the vehicle into the canal, the memo alleges.
In the state attorney's memorandum, Cusanelli said Klee was bleeding from a serious head wound and was not breathing. He told authorities he would never have put Klee's body into the van and rolled it into the canal if Klee wasn't dead, the memo says.
Carl Cusanelli told police he helped push the van into the canal, the memo says, but denied any knowledge that Klee may have been in the van at the time.
David Cusanelli also told police that he thinks he blocked the whole incident from his memory and that only recently did some details begin to materialize, according to the prosecution memo.
"It's turned their worlds upside down. They are very upset," said Polay, the defense attorney. "Thirty-one years ago, David was best friends with Jeff Klee."
Coral Springs Police Chief Duncan Foster expressed frustration that no charges are being brought.
"Jeff Klee was a loved member of someone's family, and that has no time limits," Foster said. "It's just very, very frustrating for us."
Steele, Klee's sister, said, "Victimized by the loss of Jeff so many years ago, we are victimized once again."
Klee's mother, Florence Klee, clutched a framed photo of her son but did not speak during Thursday's news conference. Klee's father died about two years ago.
Authorities said the case remains open.
The family and the police are asking for the public to help them find any possible evidence of what happened that summer night in 1977 at the canal.
"Justice has been denied," Steele said.