How to emotionally support my dad?

Hello all, I need some wisdom.

My grandpa turned 95 yesterday and he's near the end of his life. He's been deteriorating for a while, but the last couple of weeks/months have been especially rough, and it's gotten to the point where we expect him to pass by the weekend. It's been rough on the entire family but it seems to be hitting my dad especially hard.

Overall I'd say our relationship has been pretty positive in all ways except emotionally (goes for my mom too, but to a much lesser extent), and I want to be there for him. He's been exhibiting some behaviors that worry me. Short temper, aggressive driving and speeding, hiding his tears, putting on a facade; all the "usual guy stuff" when things get hard. If it's relevant he's in his 70s and I'm 29.

I've been through plenty of my own shit (trauma, mental health issues, chronic health issues, sexuality, toxic masculinity; a laundry list), I've been medicated and in therapy for a while, and I've learned a lot about how my mind works. He was on antidepressants for a while and went to therapy when my sister and I were very young (he's a doctor and had just finished residency when my older sister was born), but aside from that I don't think he's put much thought into his mental health. And things like depression, alcoholism, and other stuff runs in the family, but my grandpa and dad were both able to steer away from it (unlike a lot of our relatives). The only time I've seen him cry was when he was supporting me at a friend's funeral. He's just never been very open about any of these topics. Fair to him, but I want him to know that he isn't alone, destroy himself, or feel like he can't be vulnerable with those closest to him.

Aside from "be there for him," what has worked for y'all? Happy to provide more information or clarification, as I was half-venting while I typed this out.