Professor Ronald Bettig killed by two friends who believed they were named in his will

Danelle Geier and George Ishler have been charged in the death of Ronald Bettig, who police say was pushed off a cliff at a quarry and fell 80 feet. Photo / AP

A man and woman allegedly pushed their media professor friend off a cliff because they believed they would financially benefit from his death.

Danelle Geier, 32, and George Ishler Jr, 39, have been charged in the murder of 56-year-old , whose remains were found at the bottom of a quarry in Potter Township, Pennsylvania last week, Centre Daily Times reported.

Authorities said Ishler and Geier plotted to kill the Penn State associate professor because they believed they were named in a will he recently signed. Ishler was friends with Bettig, while Geier lived with the educator.

George Ishler Jr, 39 and Danelle Geier, 32. Photo / Centre County Correctional Facility

According to court documents, Geier and Ishler originally plotted to have Ishler drown Bettig at Rehoboth Beach in Delaware. They later came up with the plot to kill him at the quarry.

During the trip to Rehoboth Beach, authorities say, Geier texted Ishler, and made an alleged reference to being ready to kill Bettig because she was angry that he had criticised how she was raising her son.

Geier allegedly wrote, "So ready I am pissed off."

Authorities allege that the pair persuaded Bettig to travel to the quarry by telling him they could harvest marijuana there.

They allege that Geier told police that Ishler told her that the plants were so close to the edge that Bettig might fall, but if he didn't, Ishler would "help" him. Ishler then allegedly pushed Bettig, who fell 25 metres to his death, police said.

Ishler told police he heard his friend's body "crunch" when it landed, New York Daily News reported.

Geier allegedly told police that she and Ishler also agreed to stage the scene with items such as Bettig's car, water bottles, flashlight, hand rake and bag, to make it appear as if he was alone, and they agreed to report him missing three days later.

The two told police on August 15 that Bettig and his vehicle had been missing for three days and suggested that he may have gone to California, authorities said in court documents.

Geier was arraigned on Saturday night on charges of first- and third-degree murder, conspiracy, aggravated assault and evidence-tampering. Ishler has been charged with first- and third-degree murder.

According to the criminal complaint, they were "known drug users".

According to Penn State's website, Bettig joined the College of Communications in 1988 and was an associate professor of media studies. He taught courses on the political economy of communications and wrote at least two books on the subject.

"We are deeply saddened by the loss. He was a part of the fabric of this College for many years. All except our very newest faculty and staff members very likely knew Ron, who was one of our longest-tenured faculty members," College of Communications Dean Marie Hardin said.

"Ron was the kind of teacher who connected powerfully with students, who found his classes in political economy - at both the undergraduate and graduate levels - transformative."