Thank you for sharing this tragic story here on PC. Personally I think the obvious recommendation here is to have your grandson seen by a child psychologist or mental health therapist who has expertise in working with children. In the meantime, here are links to 9 articles, from PsychCentral's archives, that hopefully may be of some help. These are not going to address your grandson's situation directly. But, hopefully, the information in them can be helpful in understanding the dynamics of the situation your grandson is in & in figuring out how to address these tragic circumstances:

How to Support a Child when a Parent Suicides | Unshakeable Calm

An Open Letter to Any Child Who Lost a Parent to Suicide

Suicide: Helping Survivors Cope

Should I Talk to My Child about Suicide?

What Parents Need to Know about Childhood Depression

Child Depression and Adolescent Depression

https://psychcentral.com/lib/depress...-and-children/

https://psychcentral.com/lib/depress...ts-caregivers/

https://psychcentral.com/blog/helpin...ming-behavior/

My best wishes to you & your family...

P.S. Here's a link to another series of articles I just came upon, in PC's archives, on the subject of talking to your child about the loss of a loved one:

https://psychcentral.com/lib/talking...f-a-loved-one/