Please press charges.
My cousin is a drug addict. He raped my sister when she was eleven, sent two of his younger siblings into foster care due to physical abuse, sent the mother of his child to the hospital because he beat her up so badly (this happened in another country too), and on and on. His own mother locks the door to her bedroom every night so he doesn't attack her.
They never pressed charges. The closest they ever got was when he sent his siblings to foster care - he was a juvenile then.
When his sister got married (she wisely banned him from the wedding), we all ended up looking over our shoulder praying that he wouldn't show up and hurt somebody, including the children at the reception.
He is obviously mentally unstable, but in the US they can't institutionalize him unless he does so voluntarily. Or unless he hurts somebody who is willing to press charges.
His parents loved him at the expense of others, including their other children, who are now extremely resentful. His parents were not psychiatrists. They were not physicians. And somehow they deluded themselves into believing that their love was enough to cure him, while others paid the price.
I would presume that your mother is not a psychiatrist/social worker/physician. She wouldn't have the professional skills needed to fully assess this case. And even if she was any of the above, she would have a moral obligation to recuse herself from your brother's case.
You do not cause a division in your family if you press charges. Your brother's behavior did that. His choice to self-medicate his condition did that. You are acting in the best interests of your children, as any mother should.
He's already acted up three times. How many strikes does he need before you call him out?