According to widespread reports in Austria, Dreesen suffered a serious injury to his hand when his rifle accidentally went off on his shoulder as he was walking to his car.
Police in the country, which borders Germany, confirmed that a 50-year-old had shot himself by mistake on Thursday evening.
“The hunter in question had his rifle over his shoulder, he walked over to his car, then a shot was released with his left hand over the barrel of the gun,” a police officer told SID.
“The injuries to his fingers were severe and he may have lost some of them.”
According to the Austrian media outlet ORF, Dreesen was immediately taken to hospital where he is believed to be in a stable condition.
Dreesen, who is affectionately known as the ‘Lord of Numbers’ at Bayern, oversees finances, ticket sales and security at the Allianz Arena.
Bayern CEO Karl-Heinz Rummenigge confirmed the incident and wished his colleague a swift recovery.
“Of course we were frightened when we heard the news,” he told the club’s official website. “We’re relieved that Jan-Christian is already on his way to get better.
“On behalf of Bayern Munich, I wish for my colleague to get well very soon.”
Bayern have been rocked by a tumultuous week on and off the pitch.
After drawing 2-2 with Wolfsburg on Friday, the reigning German champions were defeated 3-0 by Paris Saint-Germain in the Champions League on Wednesday.
Head coach Carlo Ancelotti was quickly sacked after a player revolt, with Willy Sagnol installed as his interim replacement.
Bayern, who are third in the Bundesliga with six games played, will aim to bounce back to good form with a visit to Hertha Berlin on Sunday.
