Your assumption was on-target. Most investigation to date indicates cytokine storms developing in many/most COVID-19 (WHO's new official name for the disease caused by 2019-nCoV) cases that become fatal.
Knowing that may not be all that useful in a clinical sense, because there aren't really any good, established ways to deal with cytokine storms.
I don't think the fact that the fatalities are typically in older patients argues against the relationship. Remember, cytokine storms are explosive but
ineffective immune responses that develop in later-stage illness.
A Google search for "coronavirus cytokine storm" will return many of the most useful results. This Lancet brief and the papers cited in it is a good place to start and has been widely cited in the short time since publication:
https://www.thelancet.com/journals/l...305-6/fulltext