This is C.J. Twomey, a former member of the US air force from Maine who died aged 20 on 14 April 2010. He took his own life.
Hallie sent respondents a package containing a letter, some ashes, and a picture of C.J. in his Red Sox T-shirt.
More than 9,000 people have offered to help, and the ashes have been scattered in more than 100 countries.
Hallie told BuzzFeed News about the mix of emotions she's felt from so many people sharing C.J.'s memory and helping to spread his ashes around the world:
It's been the best kind of exhaustion. Seeing the response from so many people across this vast planet leaves me feeling breathless, eternally grateful and hopelessly sad all at the same time. I want my son back.
If he was here, none of this would be happening. The Scattering CJ journey will always be incredibly bittersweet for that reason. No mom wants to mail their son's ashes to anyone anywhere.
To do so means he's gone forever and that continues to break my heart each and everyday. But starting this journey for my beloved son ultimately was the right thing to do. I truly believe he would rather "see" the world then spend eternity in an urn.
His ashes have been scattered on a tea plantation in Tamil Nadu, India.
Over the Grand Canyon.
From a hot air balloon over Cappadocia, Turkey.
At Lake Windermere in England's Lake District.
In Chiang Mai, northern Thailand.
Someone scattered them while skydiving.
Someone did it while scuba diving-off the Reuben Coral Reef, near the Dominican Republic.
US snowboarder Justin Reitner scattered them during the Sochi Winter Olympics.
C.J.'s ashes even made it into space, via the New Mexico desert.
Hallie wrote yesterday that there isn't much of C.J.'s ashes remaining
She said it will take until next year for all the ashes to be sent. "Thanks again to each of you for simply taking the time to read about my beloved son," she wrote. "C.J. was awesome and I miss him more with each passing day."
She said C.J.'s ashes have yet to make it to Rio, the Galapagos Islands, and the Great Pyramid at Giza, Egypt.
Hallie said the main thing is that the project means C.J.'s memory lives on:
I know if he had lived, he would have traveled as he was always up for an adventure. I hope in some small way that this last global adventure helps ensure that C.J. won't be forgotten. He is simply worth remembering.