Fallout from the death of a French bulldog named Kokito continued for United Airlines on Thursday, as the airline explained how the dog had come to die in an overhead compartment and a U.S. senator introduced a bill to stop such a thing from happening again.

United’s admission followed an uproar over the Monday death of Kokito, who was placed in the overhead bin shortly before a flight left Houston for New York.

Maggie Schmerin, a spokeswoman for United, said the airline had spoken to the family, the flight crew and passengers who had been seated nearby. The flight attendant who placed the carrier in the overhead bin said she had not heard the owner tell her that the dog was in the carrier, Schmerin said. A witness and the owner said the dog had been barking before takeoff.

“As we stated, we take full responsibility and are deeply sorry for this tragic accident,” Schmerin said. “We remain in contact with the family to express our condolences and offer support.”

Sens. John Kennedy, R-La., and Catherine Cortez Masto, D-Nev., introduced a bill Thursday to prohibit airlines from storing animals in overhead compartments. The bill is called Welfare of Our Furry Friends Act, or WOOFF.

Meanwhile, the Harris County district attorney’s office, in Texas, told a local news outlet that its animal cruelty task force would conduct an investigation into the death. If there was one cause that Americans could unite behind, it was justice for Kokito.

Putting animals in the overhead compartment is against United’s policies. But the airline said that in April, it would start issuing brightly colored bag tags to customers traveling with pets, in order to prevent animal deaths.

In an interview with Telemundo on Tuesday, the dog’s owner, Catalina Robledo, said that she had warned airline employees the dog would be in danger in the overhead bin, but that they insisted on putting the carrier there.

French bulldogs often develop respiratory problems, partly because of the way their faces are shaped, and are prone to heart defects.

United Airlines has suffered a string of bad press since last year, when a passenger was dragged off an overbooked flight at a Chicago airport. More recently, its treatment of pets has come under scrutiny. This week, it apologized for having mistakenly sent a German shepherd to Japan.