DENVER -- A 4-year-old Palisade boy fights for his life at Children's Hospital, just two days after his 2-year-old brother died.
Some of his family members went to Grand Junction to try to gain custody of the boy from his mother, 24-year-old Heather Jensen. The hearing happens Friday.
Emergency workers speculate the boys were poisoned by carbon monoxide.
But friends of the family say that's been ruled out.
Tyler Jensen's step-grandfather said the 4-year-old had an MRI Thursday morning that showed he has severe liver and kidney damage.
But they're hopeful, he'll pull through.
What got him so sick is still unknown.
The Mesa County Cor0ner still hasn't released a cause of Tyler's brother's death.
The two brothers--so close--they'd fall asleep in each other's arms.
Now, Tyler, 4, will awaken to never again see his brother William, 2.
"Tyler is a 4-year-old little boy, full of life. He loves fishing, hiking, playing. He's a great kid. We all love him and we're all devastated about this," says the boys' step-grandfather, Robert Mathena.
They're devastated by what happened inside a red Toyota 4Runner Tuesday night outside the Powderhorn Ski Resort, east of Grand Junction.
"Patient is a 2-year-old male, not conscious, not breathing, in cardiac arrest. We have started CPR," says a dispatcher on the website Radio Reference.
Heather Jensen told police she'd left her boys inside her SUV for 90 minutes with the engine running while she met a man.
She says she sat in the man's truck next to her SUV.
When she drove away, she told police she heard her 4-year-old gurgling. That's when she stopped and realized William wasn't breathing. She called 911.
"This could be carbon monoxide. We have a 4-year-old, repeat, 4-year-old, also in the car that's having medical issues...RP (reporting party) states the breathing sounds like gurgling every breath," say the dispatchers.
Tyler is eventually airlifted to Children's Hospital.
William is pronounced dead in the SUV.
The death comes just weeks after the boy's father, Eric, died in a head-on collision Oct. 10.
"He's got a lot of love headed his way. He knows it," says Mathena about Tyler.
Tyler's family is still suffering from the loss of his father and now his little brother.
They're praying they don't lose a third loved one, in just a matter of days.
"We're praying to God. What else can you do?" says Mathena.
A medical expert says the gurgling sounds Tyler made trying to breathe is a sign of fluid in the lungs.