Investigation Into Man's First Wife's Death After Being Charged With Murder of Second

— -- A Colorado man has been charged with the murder of his wife two years ago in a national park and investigator are looking back into the death of his first wife years earlier, authorities said.

Harold Henthorn, whose second wife Toni died after falling off a cliff in the Rocky Mountain National Park in September 2012, was arrested Thursday and charged with her murder after police said they determined that they have enough evidence to argue that it was not an accident.

Now, the Douglas County Sheriff's Office has confirmed that the investigation into the 1995 death of his first wife, Sandra Henthorn, is "open and active." Sandra, then 38, died when a jack slipped while she and her husband were changing a flat tire and their car crushed her to death.

"I'm sure when all the facts are known in this difficult and complex case, justice will be done," Henthorn's attorney Craig Truman told ABC News after his client's arrest Thursday.

Henthorn, 58, was taken into custody by the FBI and the National Park Service without incident after dropping his daughter off at school and he was charged later that afternoon, authorities said. He is due back in court for a detention hearing next week where prosecutors are expected to argue that he should be held without bond.

"Today's arrest of Harold Henthorn is a culmination and validation of the efforts of some exceptional people with the National Park Service and the FBI," Toni's brother Todd Bertolet told ABC News on Thursday. "This judicial process is not only warranted, but is deserved by a wonderful lady that was my sister, Toni Bertolet Henthorn. We obviously did not choose to be placed in the position that we find ourselves, but we fully support this process in effort to seek justice for my sister."

Henthorn has maintained that his second wife's death was an accident, but the autopsy report indicates that there was some possibility that she may have died as a result of foul play.

After noting blunt force injuries on her head and neck as well as extensive abrasions, the Larimer County coroner's office concluded that her injuries were sustained "when she fell or was pushed down a cliff." They did not go so far as to make a judgment "the manner of death is undetermined."

A District Court report reviewing her estate noted that she had three $1.5 million life insurance policies at the time of her death. The Special Administrator of the Estate noted that a claim was made for one of those policies just two days after she died -- on the same morning that her autopsy was being performed -- though no payment was ever made on that claim.

Jeff Dorschner, a spokesman for the U.S. Attorney's office of the District of Colorado, confirmed to ABC News that the investigation into Toni Henthorn's death started first as a death investigation by the National Park Service since she died on federal property. That led to a criminal investigation involving the FBI and "once they made the determination that there was probable cause that [Harold] Henthorn committed first-degree murder, the U.S. attorney's office went to a grand jury to obtain an indictment."

In its news release about his arrest, the FBI asserted that Henthorn "willfully, deliberately, maliciously, and with premeditation and malice aforethought did unlawfully kill his wife."

Henthorn could face life in prison without the possibility of parole, as well as a fine of up to a $250,000, if convicted, according to the Associated Press.

"When a violent crime such as this occurs in a national park, one of our nation's most treasured places, we work hard to ensure that those responsible are held accountable," Rocky Mountain National Park Chief Ranger Mark Magnuson told the AP.

Carol McKinley contributed to this story.