Day 2: 5:00 A.M.-6:00 A.M. - S2-E22
Corrected entry: In the second series in the 5.00 - 6.00 AM episode where Kim is walking around in the house, she looks out of one of the windows, where she sees the dead police officer. It was Gary Matheson who shot the police officer, but you don't hear any sound of a shot, and in the next scenes where Kim is shooting Gary there is no silencer on the gun.
Correction: Gary Matheson did not kill the police officer by shooting him. He didn't even have a gun on him that time. The gun that Kim used to shoot Gary was the gun that Gary took from the officer after killing him. Notice earlier that Gary entered the house with the dead officer's gun-belt.