The family whose dog died after a United Airlines flight attendant forced them to put the pet in an overhead compartment is speaking out.

“He was a member of our family,” a teary-eyed Sophia Ceballos, 11, said in an interview with Good Morning America. “He was like my brother to me.”

Ceballos, along with her mother Catalina Robledo and brother, 2 months, were returning from Houston, Texas, where Robledo’s husband was working. They brought the 10-month-old French bulldog, Kokito, along for the trip.

However, the return flight to New York ended in tragedy after the flight attendant made them stow the pet in the overhead bin rather than beneath the seat in front of theirs, according to GMA.

“We were gonna put him under the seat and then the flight attendants came, she said, ‘You have to put him up there because it’s going to block the path.’ And we’re like, ‘It’s a dog, it’s a dog.’ And she’s like, ‘It doesn’t matter you still have to put it up there,’ ” Ceballos recalled on GMA. “She helped her put it up, and she just closed it like it was a bag.”

Outrage over dog's death after flight attendant allegedly orders family to place dog in bag in overhead bin. @LinseyDavis has the troubling story:— Good Morning America (@GMA) March 14, 2018

Despite the dog reportedly barking early into the three-hour trip, the pet remained in the overhead bin until the plane landed, GMA said.

“My mom got up and got the bag, and she took him out, and she’s like, ‘ Kokito, Kokito, wake up!’ and he didn’t,” Ceballos told Today in another interview, Wednesday.

“She just closed it like it was a bag.” Family speaks out after puppy put in overhead bin by attendant dies on United flight— TODAY (@TODAYshow) March 14, 2018

Fellow passenger Maggie Gremminger told PEOPLE that she was “stunned” to see the puppy being stowed in an overhead bin but understood why the family followed the flight attendant’s instruction.

“My only thought is that if it had been me, it would have been a hard scenario. The flight attendant is the authority figure, who should be trusted. I was thinking ‘maybe there is an improved ventilation system’ or something of the sorts,” Gremminger said. “Also, the owner had an infant and other daughter. Causing a scene before flight could risk being kicked off the flight. I can only imagine she felt stuck in her decision to comply.”

Gremminger said the dog stopped barking after the plane hit turbulence about 30 minutes into the flight, but his death was not discovered until the plane landed.

WATCH: Dog Dies on United Flight After Attendant Forces Passenger to Stow Pet in Overhead Bin

“A stranger offered to hold her newborn while she sat on the floor, there in the airplane aisle. She was holding her dog and rocking back and forth. Her daughter was also crying,” she explained of the scene following the discovery. “People who could not see what was happening were confused as to what was going on. I tried to encourage people to let them off first but it was confusing and so we waited for the rows to filter out. It was absolutely horrible.”

Gremminger added to PEOPLE that the flight attendant who moved the dog seemed “frazzled” and claimed that she was unaware a live animal was in the carrier.

I want to help this woman and her daughter. They lost their dog because of an @united flight attendant. My heart is broken.— MaggieGremminger (@MaggieGrem) March 13, 2018

United Airlines spokesperson Maggie Schmerin provided a statement to PEOPLE in response to the tragedy.

“This was a tragic accident that should never have occurred, as pets should never be placed in the overhead bin,” she said in the statement. “We assume full responsibility for this tragedy and express our deepest condolences to the family and are committed to supporting them. We are thoroughly investigating what occurred to prevent this from ever happening again.”

United’s pet policy online allows non-service dogs in the cabin with a service fee of $125 as long as the dog “is in an approved hard-sided or soft-sided kennel. The kennel must fit completely under the seat in front of the customer and remain there at all times.”