Can't get these hanger bolts out
The previous owners of our house had a flat screen TV mounted over the fireplace with a mounting rack and four hanger bolts. We removed the rack and want to paint over the area where it was hung, but we can't figure out how to remove these bolts. We got them to start moving with a pipe wrench, but now they're just spinning and spinning without coming out any more. They're sunk into brick, but we have no idea how long they are. Any ideas on how to get these out, short of sawing them off?
Thanks in advance!