A golf course is apologizing for advertising nine holes of golf for $9.11 on the anniversary of the Sept. 11, 2001 terrorist attacks.

Tumbledown Trails Golf Course in Wisconsin advertised the special with an ad Monday saying it was meant to commemorate the 12th anniversary of the attacks that killed nearly 3,000 people.

News of the special spread on social media, and the golf course's Facebook page was overrun with negative comments.

On Monday, the golf course apologized on Facebook and said it may close Sept. 11 out of concerns for the safety of its staff.

Club owner and general manager Marc Watts said Tuesday that no disrespect was intended. He says people are calling the club with death threats.