The Cannon House Office Building flag was at half-staff to pay tribute to victims of the Oct. 22 Nevada school shooting.
The third proclamation came Dec. 14, when 20 children and six adults were killed in the mass shooting at Sandy Hook Elementary School in Newtown, Conn. The proclamationís duration lasted for five days and was extended on Dec. 18 in honor of Sen. Daniel K. Inouye, D-Hawaii. Flags were raised again on Dec. 22.
After the Boston Marathon bombings on April 15, flags were lowered to half-staff through April 20. The six-day tribute was one of the longest in recent history. Following the Navy Yard shooting on Sept. 16, the president ordered flags to be lowered to half-staff and remain at that position through sunset on Sept. 20.