Hung is the past tense and past participle of hang in most of that verb’s senses. For instance, yesterday you might have hung a picture on the wall, hung a right turn, and hung your head in sorrow. The exception comes where hang means to put to death by hanging. The past tense and past participle of hang in this sense, and only in this sense, is hanged.
When someone is hung out of malice but with no intent to kill, as described in the example below, hung is the conventional word:
They hung him by chains and tortured him. [Day Press News]
A column of smoke visible from six miles away hung over the scene throughout the afternoon. [NBC Washington]
Two teenage boys that hung on to tree branches for two hours in the middle of Beaver Creek have been rescued. [My Fox Phoenix]
I hung the decorations in our platoon office for everyone to enjoy. [Galesburg Register-Mail]
The hangman, who has hanged nine people in his 21 years in prison, has requested anonymity. [BBC News]
A man due to be sentenced tomorrow for murdering his brother has been found hanged in his cell. [Mirror]