United Airlines is finally taking a hit after forcibly kicking a passenger off a plane

Shares of United Continental are under pressure ahead of Tuesday's opening bell, down 3% at $69.41 a share, amid the fallout from Monday's incident where a passenger was forcibly removed from a plane by airport police.

The passenger suffered injuries to his face, and was taken to the hospital for treatment, after refusing to give up his seat on an overbooked flight from Chicago to Louisville.

The incident has blown up on social media, where people are threatening to boycott United.

United CEO Oscar Munoz also released a statement after the incident:

"This is an upsetting event to all of us here at United. I apologize for having to re-accommodate these customers. Our team is moving with a sense of urgency to work with the authorities and conduct our own detailed review of what happened. We are also reaching out to this passenger to talk directly to him and further address and resolve this situation."

Despite Tuesday's selling, United shares remain just off their all-time high of $74.09 set back on February 28. They're down about 4.7% so far in 2017.