JMO, this seems to be triggered in part by his gambling addiction, on top of his somewhat histrionic personality.
Sounds like he's been gambling for a while. Went through bankruptcy already. Has probably spent many years hitting up his family, girlfriend and friends for money when he gambled his own earnings away.
His mom has probably had him come begging for money many times and has probably heard all the threats about "I'm depressed! I've (lost home, lost car, etc.) because of gambling and if you don't give me money I will kill myself." I've never personally experienced it, but have heard its terrible living with a gambling addict, at least as bad as living with a junkie. They steal, lie, beg for loans and never pay them back, etc.
Sounds like family and girlfriend finally gave him some tough love after he failed to deal with his gambling problems. His response was to behave like a spoiled child - go on a rant, talk trash on facebook, pretend everyone treats him badly, then kill an innocent old man just to get everyone's attention. He's an incredibly selfish, self-absorbed person who wants to take the lives of innocent people in order to "punish" those who stopped allowing him to use and abuse them.
I also seriously doubt he told his mother he was going to kill someone. He made that statement as a way of blaming her for his own problems, as punishment for not giving him money.
He's also unlikely to commit suicide, seems to narcissistic for that. Maybe suicide by cops or turning himself in. JMO
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