I'm currently researching trey sesler a little bit so here's a few funfacts about him:

-he had poor hygiene
-he isolated himself from his family members and friends months before the shooting
-he was planning on injuring about 70 people
-he rated certain shootings in a 1/10 scale(Kip got the lowest score)
-he was born august 3, 1989
-he did drugs

-his brother, mark, told one of his friends that he wouldn't be surprised if trey killed him
-he was 6'5
-his favorite anime was gunsmith cat
-he didn't seem to be really involved in politics but wasn't "a big fan of abortion"
-when he was 9 he saw a documentary on the+

columbine[?] shooting "about 50 times"(the wording from the article I'm reading is weird but I'm assuming they were talking about columbine)
-he said that he related to cho seung-hui
-he had planned to kill people long before the shooting(check pics bellow)

-he had a framed picture of his dead chicken in his home
-he was writing a book; “It’s about a guy that lives in an apartment with his two kids and his wife. He has a bad attitude all the time. He always says smart ass things to his kids. That’s where the comedy comes from,”

Most of the info in this thread come from this article: https://www.crimemagazine.com/mr-anime-loves-god-and-his-family
And mr anime's q and a video: