The next few hours were a bit of a blur as he stitched up his shoulder and covered his wife's body, before the wizarding police showed up. The Aurors, for their part, arrived ready to duel with dark wizards, what they were not ready for, was an angry muggle standing over two dead death eaters. After calming him down and assuring the man that they were in fact, with the law, they took him to the ministry to take his statement.
Three hours later they had verified his story, with some disbelief, and told him he was free to go. Apparently his house had been fixed and he was to tell everyone that his wife had been killed by a burglar. William was also fairly sure that they would have made him believe that was what had really happened if he wasn't already aware of the wizarding community. After he had been released, he asked one of the Aurors who had interviewed him how he could get to Hogwarts, so the man pointed him to a grizzled old man by the name of Mad Eye Moody who apparently knew Headmaster Dumbledore quite well.
Moody wasn't a bad sort, and William was rather relieved to be in the presence of someone who was so clearly a veteran of battle after the night he'd had. There seemed, to the Aurors who saw the two men, to be an ease to how they interacted, a dangerous edge to their movements that warned off anyone from getting in their way.
As they left the ministry Moody was pleasantly surprised that this muggle father was grilling him for all the information he could give on the DeathEaters, and seemed not to be taking his situation sitting down. Moody had heard of what he did two the two intruders who had invaded his house and couldn't help but think that even as a muggle, this was a man that would be useful to have as an ally, so he was more than happy to answer William's queries.
They arrived in the village of Hogsmeade the next morning, after a quick meal and were met by a stern looking witch named Professor Mcgonagall, who William recalled as the one who had given his daughter her Hogwarts letter. She must have been informed of his situation beforehand because she shot William a pitying look before ushering him into the headmasters office.
William's first impression of Lily's Headmaster was that of a caring old man, nothing more than an academic minded civilian.
His second impression sent shudders down his spine, and he quickly reevaluated how dangerous the man in front of him was. He certainly didn't want to get on the bad side of a man who could conceal how powerful he was so well. It wasn't often that William couldn't read someone, but as he looked at Dumbledore, it was only a few small things that gave the wizard away, in addition to his instincts screaming at him, he could see a tension in those shoulders and a steely weariness in his eyes that told of a leader who took the weight of the world on his shoulders.
Nonetheless, he was not here to evaluate the Headmaster, though he did feel safer knowing his daughter was under the protection of this man, there was something more important that he needed to do.
"I need to speak to my daughter, Lily Evans… to inform her of her mother's death"
He spoke coldly, with minimal emotion but his true state of mind was given away by the hitch in his voice, which all present, thankfully ignored. Dumbledore regarded him unreadably for a few moments seemingly judging his mental stability before speaking. Not that William begrudged the man for it, in fact he was rather thankful that someone had thought to check before he was given access to his daughter.
After a few more moments of scrutiny Dumbledore broke eye contact. "of course" he said
"Professor Mcgonagall will fetch Miss Evans after breakfast"