Armchair Psychology incoming!:
I think he wanted to be discovered.
I think that's why he changed his education on facebook after the murder. He knew he would get caught, and he wanted to control what people saw.
He's the black sheep in his otherwise "picture perfect" family. He's been in and out of trouble for a long time, and he's got criminal records that span multiple states. Add to that, the fact that he identifies as Christian but clearly isn't living his life to a standard that most Christians would deem appropriate, there's likely some heavy inner turmoil regarding religious guilt.
Based on his interactions on facebook, it seems that he clings really hard to people who will validate and support him, likely due to major insecurities regarding his character, behavior, and subsequent self-worth. His relationships with people are fleeting, though. His behavioral and substance issues are chronic and he always goes back to them. Those who he's been clinging to and is totally dependent on for his self-worth are disappointed. Their disappointment in him is seriously compounded by the hatred he has for himself, and it's overwhelming for him. He copes with this feeling by turning his shame into resentment towards those who are disappointed in him. He seems to spiral into patterns of dangerous and self-destructive behavior when these incidences occur. I get the feeling that it's partly because it's comforting to completely give in to being the piece of trash he feels like he is, partly because he wants to "show them!" and partly because he wants them to pity him for being so hopeless.
This is based only on the interactions I've seen him engaged in on facebook, and on some vague but telling statuses posted by family throughout the years. But if it's right....
Ingrid may went on a date or two with him last month and found him to be charming, kind, intelligent, etc. He may have been able to hide his past, and lifestyle from her during those two dates. Maybe she did some research on him before the Mariners game, or maybe something happened on their date that made Ingrid realize he wasn't really being honest about who he was, what his living situation was, and the sort of trouble he'd been in before. Whatever happened, she called him out. He was immediately ashamed, and that shame immediately transitioned to extreme resentment. This would be an absolutely devastating disappointment for him, because she's everything he's been looking for. She's gorgeous, she has money, and she's a mother (some major mommy issues there.) In a rage, he kills her. But it's sloppy, because it wasn't done with any real forethought. He knows he's going to get caught. So he moves into the "I'll show them!" stage of process. He decides to become notorious. Disposes of the body in a way that is sure to make headlines, not giving any care to covering his tracks forensically. Goes home and updates his facebook a bit for when people inevitably come looking for him. He thinks about how upset his family will be, and hopes that they'll regret not being more supportive of him and accepting. He watches the news as reports come in of a missing woman, and of a dismembered body found in a trash can. Then eventually the police come for him, and he's arrested without incident. Because this is the result he'd convinced himself he wanted.
