When Bob visits Skerritt and they embrace, Bob is clearly wearing a wedding ring which is not present in any other scene including in the continuation of this meeting. Given Bob Muldoon and Ruth Guthrie's differing names it could be presumed they are not married.
When Bob is shot while in his parked truck, he stumbles out, leaving the driver side door open. While he returns fire and confronts his assailant, he bumps into the door, causing it to close. After killing assailant and turning to get back into truck, the door is open again.
As Ruth leaves the police station after being told that Bob escaped, she unlock the drivers door with the key. But the drivers window was down. There was no need for the key.