Hi,
It sounds like he is dealing with trauma from his coworkers death.
What came to mind when reading what you shared was
Fight/Flight/Freeze responses. Persons dealing with addictions,
whether rehabilitated or not, may have one of these responses each
time they are faced with a traumatic event or even face a trigger
event that causes a response such as these listed. I think of flight
when I read your posting, as one who flees, is willing to push others
close to them away. In some extreme cases everyone in their
surroundings. This is due to a previous pattern established when
facing early trauma, etc... and can be reason one chooses to become a
user, and eventually addict.
Learning to identify the reaction pattern, and importantly to
validate our pain is critical . When we identify our triggers we can
learn new ways of responding, and coping with trauma.
A reaction in the present can often be magnified and distorted by our
experience of past events, and of events that have not and may not
happen. It is important to understand our present reactions in
context of past events.
Grounding is a great technique, especially in an overwhelming
situation such as this. It sounds like he is grieving, and needs
your understanding and space. Once he is responding to people this is
a great time to talk and support him. Forcing is not beneficial.
Healing and willingness to want to understand must come from him.
Just like when we are dealing with an addiction, we ultimately have
to leave the decisions up to them. We can help, only if they want
it, and it appears he just needs alone time to sort out how he is
feeling. Remember, we fix our own problems when we begin to
understand where the control lies. Once we see that they must take
control and want to have help, then and only then can we assist and
support, but ultimately it comes withing himself.
hope this helps.
My prayers are with you.

Nolee