Son, 28, of former Harper Collins and NBA executive Gregory Giangrande is killed in motorcycle crash along with pal as they returned from Full Moon Party in Thailand

The son of a former HarperCollins boss and his friend were killed in a horror head-on crash returning from the famous Full Moon Party in Thailand.

Elias Giangrande, 28, son of the former publishing vice president Gregory Giangrande, and his friend Jack Niehaus, 25, were riding a motorcycle back to their hotel from the beach party on Wednesday.

Police alleged they were 'drunk and speeding' without wearing helmets when they crashed into a taxi along a dimly lit road on Koh Pha Ngan island, but are yet to receive the results of blood alcohol tests.

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

Gregory - also a New York Post columnist - flew to Thailand after he was told of crash involving his son, who was a keen scuba diver and ran a luxury yachting company in Miami.

Elias Giangrande, 28, (right) the son of a former HarperCollins boss, Gregory Giangrande, (left) and his pal were killed in a horror head-on crash returning from the notorious Full Moon Party in Thailand

Jack Niehaus, 25, (pictured with his father Troy) was riding on the back of the motorcycle and was killed along with him

Jack's sister Priya Niehaus told DailyMail.com the pair were traveling around Asia with two friends and were a week into their three-week trip.

She said her brother ran out of petrol on his way back to their hotel, and Elias drove back to pick him up before they crashed.

'Think of all the best qualities of a human being, then add a cheeky joke, and a never ending smile,' she said in a joint statement with Jack's father Troy and mother Nicole.

'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. 

'A son, a brother, and most of all everyone's best friend.'

Elias with his model girlfriend Brielle Middleton on a yacht in Miami a week before his death

Photographs captured at the scene show the front of the taxi completely ripped out, in a display of the immense force the bikes crashed into the vehicle with

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.

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

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.'

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

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

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 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. 

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'.

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

Brielle commented beneath the post: 'I love u!' alongside a heart emoji, and Elias had 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.

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

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

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.

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

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

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.

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.