This April will mark the 50th anniversary of the assassination of civil-rights icon Martin Luther King, Jr. and HBO is commemorating the milestone with its King in the Wilderness documentary about the last three years of his life, USA TODAY reports.

The documentary highlights the period described as King’s most difficult time in life.

According to the news outlet, King in the Wilderness “captures the passion and fear and determination that Dr. King felt at the end of his life,” director Peter Kunhardt said in a statement.

He describes those final years as “a dark and dangerous period in the long struggle for equality. King himself described it as a time when his dream for America turned into a nightmare.”

View the trailer of HBO’s documentary commemorating the assassination of one of the world’s most prominent leaders below.