The Holocaust Museum remembered a fallen officer killed during a shooting one year ago Thursday. Officer Stephen T. Johns was gunned down by a white supremacist who opened fire inside the museum. Before opening Thursday morning, the museum held a private memorial service. More than 300 people, staff, volunteers and Holocaust survivors came to remember Johns, who gave his life to save so many others.The museum lowered flags to half staff in remembrance. A small vase of flowers sat outside the door and inside next to a plaque bearing Johns’ picture, small reminders of the deadly shooting. Officer Johns confronted the gunman at the door. For many at the museum that day, he is forever their hero.”A year later, it’s still a very painful moment for us. It’s been a year of mourning for our museum community,” said Sara Bloomfield, the museum’s director.