Grier's eldest son, Geoffrey Grier, said today that his father died at a hospice care facility in Carlsbad, a coastal city north of San Diego, after suffering a brain lesion.
Grier and Price M Cobbs, both black psychiatrists working in San Francisco in the 1960s, co-authored "Black Rage" to explain the anger that triggered the riots after the assassination of the Rev Martin Luther King Jr.
The authors argued how the heritage of slavery contributed to the unrest decades after the end of segregation and continued to affect society as well as the personal lives of African Americans.
Grier had an insatiable appetite for knowledge and was driven by his need to expose the long-lasting effects of social oppression, his friends and colleagues said.
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"I think that desire to acquire information coupled with his social conscience formed a force that was hard to be reckoned with," Geoffrey Grier said.
"'Black Rage' was required reading in schools, colleges for a long period of time. It allowed all people to be able read, understand, comprehend, draw conclusions, and make connections. It had a much larger impact than we think."
"You can try to come up with another name, call it Black Lives Matter," Grier said. "Whatever you want to say, at the end of day, there is black rage. The relevance of what they were saying is really, really on point now."
Corrie Ort said her husband closely followed the news, including the police shootings of young black men in Missouri, New York and Baltimore. The couple lived in the beach community of Leucadia, north of San Diego.