I'm confused about a scene can anyone here clarify?

I was rewatching the series on netflix for the past few weeks and I'm in the last few episodes and I get to the How Your Mother Met Me one, and it shows a scene where she walks into her apartment and theres tissues everywhere and a ukulele and she gets a phone call. It's assumed he died but what's the backstory there I feel I'm missing something. It seems like it was a sudden death with no warning which doesn't explain why theres any tissues around and it doesn't go into much detail about what was said on the phone call or where he was etc. Sorry if this is dumb but this is just bugging me and I'm sure someone on here has a better understanding. Edit: just to clarify she gets the phone call before going back to her apartment and she said she was getting a call from max so we can assume that she had caller ID and someone found his phone after he passed or something. I initially thought that he commit suicide but he seemed to be in a happy relationship and he had plans that night it wouldn't make much sense.