In the pre-dawn hours of Sunday morning, as they pulled up the long driveway that led to a cabin surrounded by pines, officials in Milledgeville, Georgia, sensed something was wrong.

Three people - a beloved University of Georgia entomology professor, a retired psychologist-turned-yoga studio owner, and a car salesman who had recently quit his job - were gathered by the swimming pool. All three were nude. The professor, Marianne Shockley, 43, was dead, and the two men were apparently trying to revive her with CPR.

"I don't know how to explain this to people who are not in our business, but when we first arrived at the crime scene, there was just something about it that was not right," Baldwin County Sheriff Bill Massee told a news conference, "and it was just sort of a bizarre, different kind of case."

Things would get even stranger before the sun came up. While waiting to be interviewed by police, Clark Heindel, the former psychologist, killed himself, authorities said. Though the 69-year-old owned the home in central Georgia where the professor was found dead, officials have said that his suicide is not an indication of guilt. Instead, they have pointed to Marcus Lillard, 41, who was dating Ms Shockley but has not admitted to playing a role in her death, and now faces murder charges.

The mystery began to unfold in the early hours of Sunday morning, when Mr Heindel, who owned a local yoga studio named Good Karma, called emergency services to report that Ms Shockley had drowned.​

World news in pictures Show all 50 1 /50 World news in pictures World news in pictures 14 September 2020 Japan's Prime Minister Shinzo Abe, Chief Cabinet Secretary Yoshihide Suga, former Defense Minister Shigeru Ishiba and former Foreign Minister Fumio Kishida celebrate after Suga was elected as new head of the ruling party at the Liberal Democratic Party's leadership election in Tokyo Reuters World news in pictures 13 September 2020 A man stands behind a burning barricade during the fifth straight day of protests against police brutality in Bogota AFP via Getty World news in pictures 12 September 2020 Police officers block and detain protesters during an opposition rally to protest the official presidential election results in Minsk, Belarus. Daily protests calling for the authoritarian president's resignation are now in their second month AP World news in pictures 11 September 2020 Members of 'Omnium Cultural' celebrate the 20th 'Festa per la llibertat' ('Fiesta for the freedom') to mark the Day of Catalonia in Barcelona. Omnion Cultural fights for the independence of Catalonia EPA World news in pictures 10 September 2020 The Moria refugee camp, two days after Greece's biggest migrant camp, was destroyed by fire. Thousands of asylum seekers on the island of Lesbos are now homeless AFP via Getty World news in pictures 9 September 2020 Pope Francis takes off his face mask as he arrives by car to hold a limited public audience at the San Damaso courtyard in The Vatican AFP via Getty World news in pictures 8 September 2020 A home is engulfed in flames during the "Creek Fire" in the Tollhouse area of California AFP via Getty World news in pictures 7 September 2020 A couple take photos along a sea wall of the waves brought by Typhoon Haishen in the eastern port city of Sokcho AFP via Getty World news in pictures 6 September 2020 Novak Djokovic and a tournament official tends to a linesperson who was struck with a ball by Djokovic during his match against Pablo Carreno Busta at the US Open USA Today Sports/Reuters World news in pictures 5 September 2020 Protesters confront police at the Shrine of Remembrance in Melbourne, Australia, during an anti-lockdown rally AFP via Getty World news in pictures 4 September 2020 A woman looks on from a rooftop as rescue workers dig through the rubble of a damaged building in Beirut. A search began for possible survivors after a scanner detected a pulse one month after the mega-blast at the adjacent port AFP via Getty World news in pictures 3 September 2020 A full moon next to the Virgen del Panecillo statue in Quito, Ecuador EPA World news in pictures 2 September 2020 A Palestinian woman reacts as Israeli forces demolish her animal shed near Hebron in the Israeli-occupied West Bank Reuters World news in pictures 1 September 2020 Students protest against presidential elections results in Minsk TUT.BY/AFP via Getty World news in pictures 31 August 2020 The pack rides during the 3rd stage of the Tour de France between Nice and Sisteron AFP via Getty World news in pictures 30 August 2020 Law enforcement officers block a street during a rally of opposition supporters protesting against presidential election results in Minsk, Belarus Reuters World news in pictures 29 August 2020 A woman holding a placard reading "Stop Censorship - Yes to the Freedom of Expression" shouts in a megaphone during a protest against the mandatory wearing of face masks in Paris. Masks, which were already compulsory on public transport, in enclosed public spaces, and outdoors in Paris in certain high-congestion areas around tourist sites, were made mandatory outdoors citywide on August 28 to fight the rising coronavirus infections AFP via Getty World news in pictures 28 August 2020 Japanese Prime Minister Shinzo Abe bows to the national flag at the start of a press conference at the prime minister official residence in Tokyo. Abe announced he will resign over health problems, in a bombshell development that kicks off a leadership contest in the world's third-largest economy AFP via Getty World news in pictures 27 August 2020 Residents take cover behind a tree trunk from rubber bullets fired by South African Police Service (SAPS) in Eldorado Park, near Johannesburg, during a protest by community members after a 16-year old boy was reported dead AFP via Getty World news in pictures 26 August 2020 People scatter rose petals on a statue of Mother Teresa marking her 110th birth anniversary in Ahmedabad AFP via Getty World news in pictures 25 August 2020 An aerial view shows beach-goers standing on salt formations in the Dead Sea near Ein Bokeq, Israel Reuters World news in pictures 24 August 2020 Health workers use a fingertip pulse oximeter and check the body temperature of a fisherwoman inside the Dharavi slum during a door-to-door Covid-19 coronavirus screening in Mumbai AFP via Getty World news in pictures 23 August 2020 People carry an idol of the Hindu god Ganesh, the deity of prosperity, to immerse it off the coast of the Arabian sea during the Ganesh Chaturthi festival in Mumbai, India Reuters World news in pictures 22 August 2020 Firefighters watch as flames from the LNU Lightning Complex fires approach a home in Napa County, California AP World news in pictures 21 August 2020 Members of the Israeli security forces arrest a Palestinian demonstrator during a rally to protest against Israel's plan to annex parts of the occupied West Bank AFP via Getty World news in pictures 20 August 2020 A man pushes his bicycle through a deserted road after prohibitory orders were imposed by district officials for a week to contain the spread of the Covid-19 in Kathmandu AFP via Getty World news in pictures 19 August 2020 A car burns while parked at a residence in Vacaville, California. Dozens of fires are burning out of control throughout Northern California as fire resources are spread thin AFP via Getty World news in pictures 18 August 2020 Students use their mobile phones as flashlights at an anti-government rally at Mahidol University in Nakhon Pathom. Thailand has seen near-daily protests in recent weeks by students demanding the resignation of Prime Minister Prayut Chan-O-Cha AFP via Getty World news in pictures 17 August 2020 Members of the Kayapo tribe block the BR163 highway during a protest outside Novo Progresso in Para state, Brazil. Indigenous protesters blocked a major transamazonian highway to protest against the lack of governmental support during the COVID-19 novel coronavirus pandemic and illegal deforestation in and around their territories AFP via Getty World news in pictures 16 August 2020 Lightning forks over the San Francisco-Oakland Bay Bridge as a storm passes over Oakland AP World news in pictures 15 August 2020 Belarus opposition supporters gather near the Pushkinskaya metro station where Alexander Taraikovsky, a 34-year-old protester died on August 10, during their protest rally in central Minsk AFP via Getty World news in pictures 14 August 2020 AlphaTauri's driver Daniil Kvyat takes part in the second practice session at the Circuit de Catalunya in Montmelo near Barcelona ahead of the Spanish F1 Grand Prix AFP via Getty World news in pictures 13 August 2020 Soldiers of the Brazilian Armed Forces during a disinfection of the Christ The Redeemer statue at the Corcovado mountain prior to the opening of the touristic attraction in Rio AFP via Getty World news in pictures 12 August 2020 Young elephant bulls tussle playfully on World Elephant Day at the Amboseli National Park in Kenya AFP via Getty World news in pictures 11 August 2020 French Prime Minister Jean Castex is helped by a member of staff to put a protective suit on prior to his visit at the CHU hospital in Montpellier AFP via Getty World news in pictures 10 August 2020 Locals harvest their potatoes as Mount Sinabung spews volcanic ash in Karo, North Sumatra province, Indonesia Antara Foto/Reuters World news in pictures 9 August 2020 Doves fly over the Peace Statue at Nagasaki Peace Park during the memorial ceremony held for the 75th anniversary of the atomic bombing EPA World news in pictures 8 August 2020 Anti-government protesters try to remove concrete wall that installed by security forces to prevent protesters reaching the Parliament square, during a protest against the political elites and the government after this week's deadly explosion in Beirut AP World news in pictures 7 August 2020 A protester throws a stone towards Israeli forces in the village of Turmus Aya, north of Ramallah in the occupied West Bank, following a march by Palestinians against the building of Israeli settlements AFP via Getty World news in pictures 6 August 2020 A woman yells as soldiers block a road for French President Emmanuel Macron's visit the Gemmayzeh neighborhood. The area in Beirut suffered extensive damage from the explosion at the seaport AP World news in pictures 5 August 2020 Damage at the site of Tuesday's blast in Beirut's port area, Lebanon Reuters World news in pictures 4 August 2020 A large explosion in the Lebanese capital Beirut. The blast, which rattled entire buildings and broke glass, was felt in several parts of the city AFP via Getty World news in pictures 3 August 2020 A general view shows the new road bridge in Genoa, Italy ahead of its official inauguration, after it was rebuilt following its collapse on August 14, 2018 which killed 43 people Reuters World news in pictures 2 August 2020 Empty stall spaces are seen hours before a citywide curfew is introduced in Melbourne, Australia EPA World news in pictures 1 August 2020 People take part in a demonstration by the initiative "Querdenken-711" with the slogan "the end of the pandemic - the day of freedom" to protest against the current measurements to curb the spread of COVID-19 in Berlin, Germany AFP via Getty World news in pictures 31 July 2020 Pilgrims circumambulating around the Kaaba, the holiest shrine in the Grand mosque in Mecca. Muslim pilgrims converged today on Saudi Arabia's Mount Arafat for the climax of this year's hajj, the smallest in modern times and a sharp contrast to the massive crowds of previous years Saudi Ministry of Media/AFP World news in pictures 30 July 2020 The Mars 2020 Perseverance mission lifts off at the Kennedy Space Centre in Florida. The mission is part of the USA's largest moon to Mars exploration. Nasa will attempt to establish a sustained human presence on and around the moon by 2028 through their Artemis programme EPA World news in pictures 29 July 2020 A woman refreshes herself in a outdoor pool in summer temperatures in Ehingen, Germany dpa via AP World news in pictures 28 July 2020 Malaysia's former prime minister Najib Razak speaks to the media after he was found guilty in his corruption trial in Kuala Lumpur AFP via Getty World news in pictures 27 July 2020 North Korean leader Kim Jong Un poses for a photograph after conferring commemorative pistols to leading commanding officers of the armed forces on the 67th anniversary of the "Day of Victory in the Great Fatherland Liberation War". Which marks the signing of the Korean War armistice KCNA via Reuters

A free-spirited entomology professor at the University of Georgia's College of Agricultural and Environmental Sciences, the mother of two was known for running an educational summer program "affectionately known as Bug Camp," her family wrote in her obituary. Deeply passionate about insects' crucial role in their ecosystems and their potential value as a food source, she would treat her students and campers to Chex Mix that featured roasted meal worms, or Rice Krispie Treats made with freeze-dried crickets.

"You're just as likely to find her in the Galápagos Islands as you are the church from her childhood," her friend Terry Jenkins told The Atlanta Journal-Constitution. "I don't think the church is going to be able to hold the amount of people that are going to come to her service."

Not long after they arrived at the house, first responders began to suspect that "this wasn't a simple case of drowning," Mr Massee said.

The professor was bleeding heavily from a head injury and emergency medical technicians got the sense that she had been dead for longer than they had been told. To deputies, something seemed odd about the way the two men, who had been friends for several years, were behaving.

University of Georgia fraternity suspended after video shared on social media shows students laughing about 'beating black people'

Mr Lillard, who identified himself as Ms Shockley's boyfriend, said that he had gone out into the woods for about 15 minutes to gather firewood. When he returned, he said, he had found her "passed out" in the hot tub. According to an incident report obtained by WMAZ, he claimed that he had pulled her out of the tub, but fell down while he was carrying her. That was how she had gotten the head injury, he claimed.

Mr Heindel seemed to corroborate that story, claiming that he had been swimming in the far end of the pool while Mr Lillard was busy gathering firewood. As soon as his friend pointed out that Ms Shockley was unresponsive, he told police, they had started performing CPR on her. Since she was still breathing faintly, they had chosen to wait 45 minutes before calling for help, he said.

To the deputies, the story about the firewood did not make any sense. It had rained heavily on Saturday and there was no chance that the sodden twigs and branches on the forest floor would have been capable of catching a spark. Also, the incident report noted, a large pile of firewood was already stacked near the pool.

Suspicious, the deputies decided to separate the two men until they could be interviewed by detectives. Mr Lillard was placed in a patrol car, while Mr Heindel was allowed to wait on the front porch.

Later, a deputy went looking for Mr Heindel to see if he knew where Ms Shockley's purse was, since the coroner needed to see her driver's license. Somehow, without any of the officers noticing, the man had disappeared. The deputy knocked on the house's front door and called out his name.

Just then, he heard a shotgun blast go off. Inside the house, he found Mr Heindel dead of a self-inflicted gunshot to the head.

"We view this as a terrible incident," Mr Massee said. "We are very sorry for his family."

Officials do not believe that Mr Heindel played any role in Ms Shockley's death, the Athens Banner-Herald reported. "This is pure speculation on my part, but maybe he was embarrassed that this happened at his house," Mr Massee told the paper.

In his obituary, the retired psychologist's family said that he had helped countless people battle their "private demons" through his work as a therapist in the Georgia prison system, and, later, his private clinical practice. "The loss of a friend on his 'watch' was a burden too great to bear," they wrote, without directly referencing the tragedy.

'I'm not going to back down' Georgia official takes oath of office on Malcolm X autobiography instead of bible

Preliminary autopsy results determined that Ms Shockley died of strangulation, not drowning. Officials did not specify what she had been strangled with.

Though a motive remains unclear, law enforcement officials think that Mr Lillard, the night's only survivor, was responsible for his girlfriend's death. Very little is known about the 41-year-old, who had worked in car sales before quitting his job earlier this month for reasons that weren't specified. Authorities believe that he had been friends with Mr Heindel for three or four years before the incident, and had started dating Ms Shockley several months earlier. It's still unclear why all three were naked when police showed up.

Mr Lillard did not make "a confession as such," Mr Massee said. But other evidence pointed to him.

For two hours before Mr Heindel called 911, the sheriff said, Mr Lillard had been texting and calling friends, asking "how to get somebody back to life." He had also allegedly queried his friends about whether they knew CPR and begged for help.

"The timeline was totally inappropriate with when we should have been called," Mr Massee said.

Mr Lillard has been charged with murder, aggravated assault and concealing a death, all felonies, and is being held without bond. It was not immediately clear if he had a lawyer.

"I will tell you this," the sheriff told reporters on Monday, "it's one of the strangest cases that we've ever worked."