NEWTOWN, Conn. — The gunman behind the Connecticut elementary school massacre stormed into the building and shot 20 children at least twice with a high-powered rifle, executing some at close range and killing adults who tried to stop the carnage, authorities said Saturday.

He forced his way into the school by breaking a window, officials said. Asked whether the children suffered, Chief Medical Examiner Dr. H. Wayne Carver paused. “If so,” he said, “not for very long.”

The terrible details about the last moments of young innocents emerged as authorities released their names and ages — the youngest 6 and 7, the oldest 56. They included Ana Marquez-Greene, a little girl who had just moved to Newtown from Canada; Victoria Soto, a 27-year-old teacher who apparently died while trying to hide her pupils; and principal Dawn Hochsprung, who authorities said lunged at the gunman in an attempt to overtake him and paid with her life.

The tragedy has plunged Newtown into mourning and added the picturesque New England community of handsome Colonial homes, red-brick sidewalks and 27,000 people to the grim map of towns where mass shootings in recent years have periodically reignited the national debate over gun control but led to little change.

Faced with the unimaginable, townspeople sadly took down some of their Christmas decorations and struggled Saturday with how to go on. Signs around town read, “Hug a teacher today,” “Please pray for Newtown” and “Love will get us through.”