“reasons”? Not to over simplify but that sounds like the drugs talking? Took her how many days to sober up enough to say that cheepshat? Maybe the kid shot the wrong mother———?
The “father” said as much by saying that the kid should have shot him instead. 100% agree.
That might make some sense psychologically. You know the old saying “Even bad men love their mothers.”
What do you do when you also hate your mother more than anyone? Hurt others.