The former sister-in-law of a man who has been charged with the murder of his second wife and is being investigated over the mysterious death of his first wife has said that she feared she might have been next. Henthorn was charged with the murder of second wife, Toni Bertolet, 51, last November and police have reopened their investigation into the suspicious death of his first wife, Lynn Rishell, some 20 years earlier. In both cases Henthorn was named as the sole beneficiary in a string of lucrative life insurance policies totaling $500,000 on the death of his first wife and $4.5million on the death of his second. And Lynn Rishell's brother's wife, Grace Rishell, has opened up to say that the FBI told her about a secret $400,000 life insurance policy Henthorn had taken out on her, too. Scroll down for video . Grace Rishell was Herald Henthorn's first wife Lynn Rishell's sister-in-law. She said that the FBI told her about a secret $400,000 life insurance policy Henthorn had taken out on her . Henthorn (left), pictured with Grace (center) and Lynn (right) Rishell, was named as the sole beneficiary in a string of lucrative life insurance policies totaling $500,000 on the death of his first wife and $4.5million on the death of his second after they both died in what appeared to be freak accident . He had forged her signature and made himself the sole beneficiary on the policy, Rishell told CBS's 48 Hours. 'That was his doing. I did not authorize that policy,' she said. 'He profits, not my girls. I feel he came in and just preyed on my vulnerability.' Both of Henthron's wives died in 'freak' accidents to which Henthorn, 59, was the sole witness. Dr Toni Jill Bertolet plunged 140ft to her death shortly before her 12th wedding anniversary while hiking with Henthorn in a remote stretch of Rocky Mountain National Park. Lynn Rishell - his first wife - was crushed to death under the front of Henthorn's Jeep when, he told first responders, the jack gave way as she reached under the vehicle for a lug night while changing a flat tire in the dark. 'I think it's logical to conclude that he was planning on taking my life at some point,' Grace Rishell said. 'He's a dangerous man... He needs to be behind bars.' Grace Rishell was going through a divorce and ‘concerned for her financial stability,’ when she initially agreed to Henthorn taking out a policy that would pay $50,000 to Grace’s brother and each of her four daughters for a total of $250,000. Lynn Rishell - Henthorn's first wife - was crushed to death under the front of Henthorn's Jeep when, he told first responders, the jack gave way as she reached under the vehicle for a lug night while changing a flat tire in the dark . Henthorn's second wife, Toni Jill Bertolet, plunged 140ft to her death shortly before her 12th wedding anniversary while hiking with Henthorn in a remote stretch of Rocky Mountain National Park . According to prosecutors in Bertolet’s murder case, ‘the evidence will show that Henthorn had a romantic interest in Rishell’. But Rishell had a change of heart in spring 2010 and told the insurance agent to stop the policy from going through. Instead she took out a policy of her own with another insurer. Unbeknownst to her ‘her signature was forged to procure the original policy as well,’ with Henthorn making payments on the policy until December 2012 and listing himself as sole beneficiary. The policy was cancelled in 2013 when the insurer concluded that Henthorn had no insurable interest in Rishell. But the very fact of its existence raises the specter that Henthorn had Rishell in his sights as a third potential victim. Henthorn was arrested on November 6 when FBI apprehended him as he returned home after dropping his nine-year-old daughter, Hayley, at school. His indictment was the result of a prolonged investigation during which the FBI eavesdropped on his telephone conversations, combed through his finances, scrutinized his employment history and concluded that the ‘freak’ hiking accident that claimed the mother-of-one’s life was murder. Henthorn was charged with the murder of Bertolet, 51, last November and police have reopened their investigation into the suspicious death of his first wife, Lynn Rishell, some 20 years earlier . Henthorn and Lynn Rishell when he was a new geology graduate from Virginia. The couple moved to Colorado, where after 12 years of marriage, she died in a 'freak accident', now said to be murder . He was denied bail by US District Judge Kathleen Latoyfa who described him as a ‘danger’ and said, ‘there are rather glaring similarities between the loss of his first wife and the loss of his second’ and pointed to large sums of money recently transferred by Henthorn to his brother as suggestive that he was ‘hiding funds.’ Though Henthorn claimed to work as a fundraiser for a charity the economic crime auditor for the US Attorney found no evidence that the geology graduate from Virginia had any earnings other than some in 1993, 1999 and 2000. The only job he appears to have had was one briefly held in the petroleum industry – the job that saw him and his then new bride, Lynn Rishell, move from their hometown of Harrington, Virginia, across the country to Colorado. The prosecution’s case against Henthorn highlights the similarities between both his wives’ passing – not least the substantial windfall both saw him set to receive. Both ‘freak accidents’ occurred at remote locations with Henthorn the lone witness. Both occurred after about 12 years of marriage and Henthorn told wildly varying stories about both deaths. Both ‘freak accidents’ occurred at remote locations with Henthorn the lone witness. Both occurred after about 12 years of marriage and Henthorn, pictured here with his first wife, Rishell, told wildly varying stories about both deaths. An autopsy carried out on Bertolet concluded that she ‘died as a result of multiple blunt force injuries when she fell or was pushed down a cliff’ According to prosecution documents Henthorn even told a Sunday school class that his first wife died of cancer and that she lost a baby she was carrying to chemotherapy. In the case of his second wife, two years before her death Bertolet almost died when she was struck by a wooden beam Henthorn had thrown off the deck of their cottage. After that incident Henthorn joked to friends, ‘I was trying to kill my wife.’ Investigators have also established that Henthorn ‘extensively scouted’ the fatal hike trail. Contrary to what he told law enforcement he made nine different trips to the area around Rocky Mountain Park that summer. The fortnight before their anniversary – the date of her death – Henthorn had hiked six trails to ‘find the perfect one for the trip.’ And damningly a map found in his car showed the spot where Bertolet fell to her death, marked with a pink X. In both  Rishell and Bertolet’s deaths Henthorn was eager to have his wives’ bodies cremated quickly despite family requests against it and, disturbingly, he spread both women’s ashes on the same mountain near Ouray, Colorado. A hearing for the civil case is scheduled for later this month while a trial date of May 4 -15 has been set for the murder case of Bertolet to which Henthorn has entered a not guilty plea.
In November Harold Henthorn was charged with murdering his second wife in criminal trial which will also hear that he killed his first wife.
Both died in freak 'accidents' to which he was sole witness and FBI spent months investigating second death before he was charged.
In both cases, Henthorn was the sole beneficiary in a string of lucrative life insurance policies.
His first wife's sister-in-law, Grace Rishell, said that Henthorn took out a $400,000 life insurance on her.
Henthorn reportedly forged her signature and made himself sole beneficiary.
Rishell believes she could have been the next to die in 'freak accident'