A dog died on a United Airlines flight Monday after a flight attendant insisted that the dog be stored in its carrier in an overhead bin.

The incident happened on a flight from Houston Intercontinental Airport to New York’s LaGuardia Airport, The Points Guy reports.

A passenger boarded the flight with the dog inside a TSA-compliant pet carrier. Once the dog was in the overhead bin, the passenger said the dog was barking for part of the flight. At the end of the trip, the passenger discovered that their dog had died.

United Airlines said they take full responsibility for the incident. The company’s policy for pets traveling in cabin is to have them in a pet carrier that fits completely under the seat in front of them and remain there throughout the flight.

“This was a tragic accident that should never have occurred, as pets should never be placed in the overhead bin,” United said in a 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.”