Brian Thompson, the CEO of UnitedHealthcare, was shot and killed by a masked man near a Midtown Manhattan hotel early Wednesday, according to police sources.

The shooting appears to be targeted but police do not know why, sources said.

Thompson was not staying at the Hilton outside of which he was shot, sources said.

Thompson was in New York City for an investors conference and his schedule was widely known, police sources said.

The gunman, who was wearing a ski mask, fled down an alleyway near West 55th Street and remains at large, police said.

The suspect is described as a skinny man wearing all black who stands at about 6-foot-1, police said.

UnitedHealthcare's parent company is UnitedHealth Group, the largest health insurer in the country.

This is a developing story. Please check back for updates.