Denver police say a hammer-wielding man shot by an officer Sunday afternoon had an apparent suicide note on him.The confrontation happened about 1:30 p.m. in a parking lot behind a Kmart at 2770 W. Evans Ave., Denver police spokesman Vicki Ferrari said.An officer was sitting in his parked patrol car completing paperwork when the man approached and tried to attack him with a hammer, Ferrari said.The officer fired on the man, striking the suspect at least once, Ferrari said. It was unclear whether the officer fired from inside or outside the patrol car. The driver-side window of the patrol car was shattered.The man was in critical condition at Denver Health Medical Center on Sunday night, Ferrari said. The officer was not injured.Ferrari said investigators found a "suicide-type" note on the man and a machete inside the man's rental car parked near the scene.While police haven't confirmed the wounded man's name, Ferrari said they believe he's a parolee with an extensive criminal record.Witness Daniel Denava said he saw the aftermath of the shooting."I saw a guy on the ground and a cop holding him at bay with his service revolver," Denava said. "It kind of shocked me."The hammer lay on the pavement a few feet from the patrol car. Investigators, including Denver district attorney officials and crime-scene technicians, spent hours combing the shooting scene.Witnesses and the officer were being interviewed, Ferrari said.