(CNN) — The CEO of UnitedHealthcare was shot and killed in midtown Manhattan on Wednesday morning, a law enforcement official tells CNN. Brian Thompson was walking toward the New York Hilton Hotel in Midtown Manhattan, dressed in a suit and tie, to attend a UnitedHealthcare conference being held in the ballroom. A gunman, who investigators tell CNN was waiting for some time before Thompson’s arrival, opened fire from 20 feet away firing multiple times, striking Thompson. Details on the circumstances are not immediately clear, but investigators say it appears to be a targeted shooting. UnitedHealthcare is the largest single health carrier in the United States and has a significant presence in Indiana, employing approximately 3,600 Hoosiers. Its Indiana Hoosier Care Connect provides coverage for members who are aged, blind or disabled, including children in foster care, and wards of the State. CNN has reached out to UnitedHealthcare for comment. This is a developing story and will be updated.