A group of senators is demanding a “full accounting” for the removal of a passenger from a United Airlines flight earlier this week, stating that the “images and emerging accounts of this incident are very disturbing.”

In letters to United CEO Oscar Munoz and Chicago Department of Aviation commissioner Ginger S. Evans, the U.S. Senate Committee on Commerce, Science and Transportation stated, “The last thing a paying airline passenger should expect is a physical altercation with law enforcement personnel after boarding, especially one that could likely have been avoided.”

The lawmakers’ letter to United says the company’s response to date “has been unsatisfactory, and appears to underestimate the public anger about this incident.” It was unclear if the lawmakers sent the letter before or after Munoz’s latest comment on the situation, in which he said “no one should ever be treated” the way David Dao was when he was dragged from his seat on an overbooked flight Sunday. One of the Chicago aviation officials who removed Dao has been placed on leave.

Also Read: United Airlines Has Already Lost $600 Million in Market Value Today

The senators asked for a response by April 20th to a series of questions about the case. They include Senate Commerce Committee Chair Sen. John Thune (R-South Dakota) and ranking member Sen. Bill Nelson, a Florida Democrat, as well as Missouri Republican Sen. Roy Blunt, chair of the subcommittee on Aviation Operations, Safety and Security, and the subcommittee’s ranking member, Washington Democratic Sen. Maria Cantwell.

The dragging incident — which culminated in a bloody-faced Dao repeatedly uttering “Just kill me” — has been a PR disaster for United, which saw its market value plunged by $600 million on Tuesday after people on social media and talk show hosts including Jimmy Kimmel and Ellen DeGeneres used the airline as a piñata.