His mother, Michelle Thompson Simard, wrote on a GoFundMe page that Jacob has been admitted to the Barbara Bush Children's Hospital in Portland, Maine, "for the last time."
She wrote earlier this month that "his father, Roger, and myself have been told that we should be spending as much time as possible with him and we should start making arrangements for his passing."
She added: "It is expected Jacob may pass away within the month."
So the boy's family, friends and complete strangers are bringing an early Christmas to the terminally ill boy - decorating his hospital room with a tree, requesting a special visit from Santa Claus and showing him support with homemade holiday cards that are pouring in from people all over, according to NBC affiliate WCSH.
"Jacob loves Christmas," his father, Roger Guay, told the news station, encouraging people to continue sending him cards. "Any way to brighten his day would be a great benefit to him."
Jacob's mother said her son was admitted to the hospital Oct. 11 after starting a round of chemotherapy and radiation, with no signs that it was helping him.
"Since then we have learned that his hip is extreamly peppered by tumors, which was described as looking like lace. This obviously has added to the pain and more importantly with his ability to walk and move around," she wrote.
Thompson Simard has been documenting the response from people who have been sending Christmas cards and toys to make the early holiday memorable for the boy.
On Wednesday, she posted a picture of Jacob with his first card, featuring a penguin, which his family says is his favorite animal.
His mother told Good Housekeeping that his motto is "live like a penguin," which, she said, her son believes means to "be friendly, stand by each other, go the extra mile, jump into life and be cool."
"Jacob loves the holiday season," she said, "and we want him to know that Christmas wishes come true and that there are good people who care all around the world."
Barbara Bush Children's Hospital said in a statement Thursday that the response has been "wonderfully overwhelming."
However, the hospital said: "Out of concern for Jacob and all the patients at the Barbara Bush Children's Hospital, please refrain from personally delivering cards to the hospital. Instead, homemade cards can be mailed to Jacob, care of The Barbara Bush Children's Hospital at Maine Medical Center, 22 Bramhall Street, Portland, Maine, 04102. Any toys or other gifts sent will be donated to the holiday gift pool for all patients at BBCH, at the request of Jacob's parents.
"Jacob and the other children at the hospital would love it if you upload videos to this Facebook page of your families or friends singing holiday carols. We will show them to the children!"
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Story by Lindsey Bever