Ex-NBA exec's son was vacationing in Thailand with TikTok star Daniel Mac when he and pal were killed in head-on motorbike crash - as heartbroken family question police report and reveal pair's last hours

Two American boys killed in a horror head-on motorbike crash in Thailand were on a three-week adventure with their TikTok star friend.

Elias Giangrande, 28, and Jack Niehaus, 25, died instantly when they collided with a minivan taxi after leaving the famous Full Moon Party on Wednesday.

Jack ran out of petrol on the way to their hotel on Koh Pha Ngan and Elias came back to give him a lift along the narrow, dimly lit road about 4.30am.

Local police alleged they were 'drunk and speeding' without wearing helmets, but are yet to receive the results of blood alcohol tests.

Elias, son of former NBA executive Gregory Giangrande, and Jack were holidaying with TikTok star Daniel Macdonald, known as Daniel Mac online, and a fourth friend.

Daniel posts skits and luxury car reviews for his 14 million TikTok fans and 2.6 million Instagram followers. He flew home to Los Angeles soon after the crash.

 Elias Giangrande, 28, was killed in a motorbike crash in Thailand as he and a friend drove back to their hotel from the famous Full Moon Party

Jack Niehaus, 25, (pictured right with his sisters Natalya and Priya) was the passenger on the bike when it collided head-on with a minivan taxi and both were killed instantly

Elias Giangrande, 28, (right) the son of a former HarperCollins boss and NBA executive, Gregory Giangrande, (left) 

Jack's sister Priya Niehaus said her family last saw him alive in an Instagram story Daniel posted about two hours before the crash.

'He was at the party and there was a jump rope with fire on it and he was jumping over it, smiling and laughing, really happy,' she told DailyMail.com.

Priya said the four close friends often traveled together and left on April 17, starting in Taiwan and planning to go to the Philippines and Japan after Thailand.

'He used all his vacation days and they were going on a three-week adventure through Asia,' she said.

'They love traveling together, they tried to go to Burning Man but couldn't get tickets.'

Gregory Giangrande, former vice president of HarperCollins and a New York Post columnist, flew to Thailand as soon as he heard about the crash, and is overseeing the repatriation.

'He's getting our boys home safe,' Priya said. 'He's unable to speak very much, he's in tears, like us he's not doing well. His wife didn't come, she just can't.'

The bodies spent days sitting in 'horrible, awful conditions' at a rescue center, and the small remote island doesn't even have a proper police station.

Elias and Jack were holidaying with TikTok star Daniel Macdonald (pictured), known as Daniel Mac online, and a fourth friend.

Daniel posts skits and luxury car reviews for his 14 million TikTok fans and 2.6 million Instagram followers. He flew home to Los Angeles soon after the crash

Priya questioned whether the pair were really drunk driving, as the police alleged, as the toxicology report was not yet completed.

'They're both very smart boys, they don't usually do anything dangerous,' she said.

'Elias was always the first to come help people and that's why he came to help my brother.'

The pair met through Daniel, who studied abroad with Jack and later introduced them about three years ago. 

The last time Jack's family saw him together alive was his 25th birthday on March 21, just a few weeks before his death.

He visited the family home on Bainbridge Island, Washington, from his home in Seattle and had dinner with Priya, his parents Troy and Nicole, and his grandmother.

Troy saw him the day he left, when he talked about how excited he was for the trip as he had never been to Asia, and was particularly keen to see Japan.

The bodies were moved from the small island to the Thai capital Bangkok on Friday, from where they will be repatriated to the US.

Jack's remains will be cremated at a Buddhist ceremony, but Elias' family was yet to decide what to do with his body.

Koh Pha Ngan police said they received a report about the crash at 4.30am. The Full Moon Party, which happens once a month, took place on April 23

The wrecked Yamaha Aerox motorbike that Elias and his friend had been riding was in a mangled heap nearby and their bodies were sprawled on the ground

Jack's family described him as 'a son, a brother, and most of all everyone's best friend'.

'Think of all the best qualities of a human being, then add a cheeky joke, and a never ending smile,' they said.

'He had an aspiring career in private wealth at UBS, but his passions were travel, racing, and he dreamt of having a family of his own.

'Jack had a positive impact on everyone he encountered, and we will miss that, along with his selflessness.

'He was a ray of sunshine no matter the circumstances and most of all he was inclusive, loving, and kind to all. He may have only had 25 years, but man were those years a true gift.'

Jack Niehaus is a wealth management associate at UBS bank who previously worked as a client service associate for investment company Morgan Stanley. 

Jack's sister Priya Niehaus said her family last saw him alive in an Instagram story Daniel posted about two hours before the crash

Priya questioned whether the pair were really drunk driving, as the police alleged, as the toxicology report was not yet completed

Jack  (pictured with his father Troy) visited the family home on Bainbridge Island, Washington, from his home in Seattle and had dinner with Priya, his parents Troy and Nicole, and his grandmother

Elias spent three years living in Europe, Southeast Asia and Central America teaching scuba diving before returning to the US to run a luxury yachting company in Miami.

His most recent post on Instagram was uploaded just one week ago, showing him and his model girlfriend Brielle Middleton in a series of sunny spots with the location tagged: 'Everywhere'. 

Brielle commented beneath the post: 'I love u!' alongside a heart emoji, and Elias responded: 'I love you too!'

The model, designer, and business owner has not yet spoken about the death of her boyfriend and did not answer calls on Friday.

Colonel Panya Niratimanon, superintendent of the Koh Pha Ngan Police Station, said cops inspected the scene and found a Toyota pickup truck converted into a passenger vehicle with a shattered windshield and damaged hood.

Photographs from at the scene showed the front of the vehicle completely ripped  out, showing the immense force the bikes crashed into the taxi with.

Horror images also showed the wrecked black and yellow Yamaha Aerox motorbike that Elias and Jack were riding in a mangled heap nearby and their bodies were sprawled on the ground.

The two shirtless American tourists were both pronounced dead at the scene, while taxi driver Supachai Lertsak, 44, was waiting for authorities.

Elias, pictured last year with girlfriend Brielle Middleton, who has not yet spoken out on the recent death of her boyfriend

 The model, designer, and business owner has not yet spoken about the death of her boyfriend and did not answer calls on Friday

Elias' mother, Sheila Hultgren Giangrande (pictured) works closely with charity Lifeline 

Lieutenant Suteep Chadakan, Deputy Inspector General of the Koh Phangan Police Station, said he was still waiting for blood alcohol test results from the hospital.

'We believe they were [drunk] because they were returning back home from the Full Moon Party,' he said.

'As for the songthaew driver, he was not drunk. The police conducted an investigation by performing a breathalyzer alcohol test at the scene, but no alcohol was detected.

'As for the CCTV cameras, the files are still being recovered. That area was very dark. It is expected that the incident cannot be clearly seen.

'From the interrogation, it was found that both the minibus driver and the deceased were speeding and collided with each other.

'The deceased drove into the lane of a minibus. The remains of both vehicles were scattered within the lane of the minibus.

'The bodies are now with the rescue team. Officials have coordinated for the family to come pick up the bodies.'

The taxi driver was detained for questioning and claimed both he and the tourists were speeding at the time of the accident.

Police said they collided when the motorcycle driven by Elias veered into the oncoming taxi's lane.

The tourists' bodies were taken to the Koh Pha Ngan Hospital for autopsies, and are on their way to Bangkok to prepare for repatriation.

Officials said they were coordinating with the US Embassy in Thailand to help the families of the deceased bring the bodies home.

Elias pictured with his girlfriend Brielle in January, three months before he died in a horror bike smash in Thailand earlier this week

Elias spent three years living in Europe, Southeast Asia and Central America teaching scuba diving before returning to the US to run a luxury yachting company in Miami

Elias Atticus Giangrande was an 'experienced yachting and diving instructor', according to his business website Captain is on Call.

The boating enthusiast had a USCG 200-Ton Masters qualification, and was also a scuba and Zapata Racing Team Flyboard instructor. 

Elias is the son of Gregory Giangrande, who is currently the Global Chief People and Communications Officer of Ellucian, a private Education Tech company.

Gregory works as a career advice writer for the New York Post, with his widely recognized GoToGreg column.

He is also a weekly on-air contributor for IHeart Radio WOR 710 talk show with Len Berman and Michael Reidel and frequent television on-air contributor for Good Day NY on Fox5 News.

Gregory was formerly the senior vice president and chief human resources officer for HarperCollins Publishers.

Elias' mother, Sheila Hultgren Giangrande, was last year photographed at the Lifeline New York Benefit Dinner at the Explorers Club, alongside Crown Princess Katherine of Serbia, and Crown Prince Alexander of Serbia - an event also attended by her late son.

Gregory Giangrande, who is currently the Global Chief People and Communications Officer of Ellucian, a private Education Tech company, also works as a career advice writer for the New York Post, with his widely recognized GoToGreg column

Daniel Mac (pictured) introduced Elias and Jack about three years ago after he studied abroad with Jack

Lifeline Humanitarian Organization is an international humanitarian organization founded in 1993 in response to the tragic situation in the former Yugoslavia, which was plagued by conflict and sanctions. 

Lifeline's mission is to alleviate and relieve the suffering of physically and mentally disabled children, orphans, and the elderly and improve medical facilities throughout the country. 

The Thai Full Moon Party is an all-night beach party on the island of Ko Phangan. 

The party takes place on the night of, before, or after every full moon that is usually attended by hundreds of backpackers.

However, the event has become a notorious celebration filled with drugs and booze, with marijuana now legal on the island.