(Des Moines, IA) -- An investigation's underway after a police officer shoots a woman with a knife in downtown Des Moines. Police say they were called to the 1400 block of Walnut Street Tuesday evening where a man said a woman was trying to stab him. Police say an officer tried to get the woman to drop the knife but she didn't, causing the officer to shoot her. The woman was taken to the hospital in unknown condition. The officer who pulled the trigger is on administrative leave while the case is being investigated.