PGA Championship -- K-9 Down ... Sheriff's Dog Dies in Hot Car

The PGA Championship was hit by tragedy -- a Sheriff's K-9 overheated in a patrol car and died in the line of duty.

The Brown County Sheriff's Office says the dog, named Wix died when he was left in a patrol car assigned to golf tournament being held in Kohler, Wisconsin. The Sheriff says the engine was running while Wix was in the car ... but the AC unit failed. Wix's partner Deputy Lemberger eventually found him unresponsive.

The AC wasn't the only problem -- according to the Sheriff the car's K-9 heat alarm also failed. We're told the system is supposed to put the windows down and sound an alarm when the car temp gets too high. An investigation has been launched.