Michael Davidson, the 44-year-old cardiac surgeon shot twice Tuesday at Boston’s Brigham and Women’s Hospital, has died. Davidson, who in addition to working at the hospital was an assistant professor at Harvard Medical School, was shot by a lone gunman and eventually succumbed to his injuries. The shooter, who also died in the incident, has been identified as Stephen Pasceri. He was found dead of a self-inflicted gunshot wound, according to police. The reason for the shooting, which took place on the second floor of the Shapiro Cardiovascular Center, is not yet known, but police believe the victim was specifically targeted. “We know he came into the hospital on the second floor, asking for this particular doctor,’’ said Police Commissioner William B. Evans. “There was a particular reason he targeted this doctor.... Right now we’re looking into the possible motive of it.” Police said Pasceri was not a patient of the doctor, the Associated Press reports.