I spoke to some police officers about this, and they were not sympathetic to the officer. Essentially stating that he was stupid, and the mistakes were due to his inexperience. They also commented that new officers need to spend more time working with a seasoned officer before being released to work on their own - and that police departments do a poor job of this.
One offered that he had a virtually identical call - welfare check on a house where a neighbor was not supposed to be home, yet the lights were on. He parked in front of the house, and ran the plates on the car in the driveway. The results gave him a name and an address that matched the home. By that time, a second officer arrived, and they knocked on the door and announced themselves - one just to the side, and another in the yard where he could offer cover. Neither used flashlights, or drew their weapons (although they were ready to do so). The occupant came to the door, said he came home from vacation early, and gave his name (which matched the car registration). The second officer then spoke to the neighbor (who had come outside). The officers thanked the resident, the resident was grateful, and the neighbor relieved. The officers were available within 5 minutes of arriving on scene.