How do you grieve?

So I’ve been talking to this guy for about 6 or 7 months. We’ve been pretty close but he has A LOT of trouble opening up about his feelings and emotional burdens… well….his mother got sick some months back…. Breast cancer. . .I would always try to encourage him to open up and tell me about how he feels but he says it’s just hard because talking about these things makes him feel worse. So he doesn’t talk about it….which to me just seems more like he’s avoiding it….well whatever right? So out of respect to him, I don’t pry or try to force him to talk if he’s not ready but I also feel like that’s damaging at the same time….when I ask how his mom is doing he’ll just reply with “fine” or I ask how he’s holding up with all of this and “I’m fine” “my days been good” etc just down plays this whole thing….sooooo everything’s fine right??? Well…a week ago today he stopped messaging me. We were having a normal conversation and we were on good terms and he asked me about a job opportunity I recently had but that was it….nothing…. Mid conversation just disappeared like that…….it’s been a week now. I’ve tried calling and texting but none of it is going through….his phone is shut off….this leads me to fear for the worst. Did his mom pass? I know he shuts down like that….. We work together and he hasn’t even shown up to work….people are asking me if I’ve seen him but I haven’t even heard anything. He had an important interview for a position he’s been fighting tooth and nail to get and was so happy just to be offered the interview that he almost cried…..but he didn’t show up. He missed it…..He just disappeared…..something tells me his mother has passed and he’s shutting down. Ignoring his phone and everyone….I understand that but .it’s pretty frustrating because I feel like at this point he should be able to tell me that. Or at least text me “stuff came up I’ll get back to you.” But no???? Nothing at all…..i hope he’s ok but the way he went about that is so annoying because I feel like I meant more to him than just ignoring me for a week no warning…..I open up to him so much and bare myself but i get ignored in return. I know I’m sounding selfish but it’s incredibly frustrating how he can just leave me out in the cold….I thought we were close but I’m just as clueless as our coworkers that he hates…….don’t get me wrong: he does make an effort to open up about things here and there so I guess it’s him trying that matters. I’m writing this because I want to learn and understand how people grieve and if anyone has any relevant experience that may help me gain insight….i’ve never lost anyone close to me before and him downplaying everything makes even more difficult to actually understand what’s REALLY going on… …..he plays it off like everything is fine and I hate that. I just wish he would let me in.