The attacker entered the office of a district governor, presented a letter then detonated himself.

A suicide bomber attacked a district governor’s office in northern Afghanistan, killing the governor and two others on Thursday, police said.

The attacker entered the office of Abdul Wahid Omerkhail, governor of Chardara district,presented a letter then detonated the bomb. The two others killed were identified as civilians, one of them a local community elder, Abdul Rahman Aqtash, the deputy provincial police chief, said.
"The district governor and two of his companions have been killed. Five other people were injured," Aqtash said, adding that the attacker was a suicide bomber.
Chardara district lies in the northeastern troubled Kunduz province, which has been increasingly affected by a conflict originally rooted in the south.