We'll see, but I'm not convinced he cared about being caught. And, though still not all that much information to go by, I'm not so sure he'd care about the death penalty.
In the PCS, it's stated that the sister says she invited AW over. Whether AW was fishing for an invitation is an open question.
There was a pattern of trouble, he made statements on FB (whether honest or not) claiming to have some emotional issues, he was directed to treatment programs & counseling, and in his witness interview he talked about how his family has mistreated him. The combination of these things, along with SM activity that is not permitted to be discussed here, has had me thinking for awhile now that this might have been some sort of act of revenge for what he deems in his own corrupted head* to be some wrong that his family or someone in his family inflicted on him. And by some wrong - it may not have been a single particular event, but a pattern over time, or even just a difference in the circumstances of his life from those of others in his family. If this is the case, I would think it's one or more of three family members--again, in his own corrupted mind*--who he was targeting with this act of revenge--his mom, his sister, and his niece, with the latter being the least likely, but still conceivable (because, for example, in his twisted mind she stole away his sister's and mother's attention from him).
All just brainstorming/speculating out-loud. I don't necessarily think this is the most likely motivation, just a possibility given the limited information so far. Of course there is so much more that we don't know.
DISCLAIMER - I'm in no way intending to blame anyone in AW's family for what he apparently did. Just brainstorming/speculating about the twisted-ness that might have been going on in AW's head.