Roy Cohn had always been a haunting presence in filmmaker Ivy Meeropol’s life, but the full extent of his existence was only apparent after she watched Meryl Streep play her grandmother, Ethel Rosenberg, in HBO’s 2003 “Angels in America.” “I think seeing the film made me finally connect emotionally to my human story, and this was a story I needed to tell,” Meeropol says. “I could do something no one else could because of my family history.”

The result is the documentary “Bully. Coward. Victim. The Story of Roy Cohn,” which debuts June 19 on HBO. 

Cohn was one of the most ruthless lawyers in American history — working with Sen. Joe McCarthy during the anti-Communist Army-McCarthy hearings of the 1950s. Cohn was also responsible, with McCarthy, for creating the Lavender scare of the ’50s, leading the government to repress and purge itself of homosexual people. And he pushed hard for the death penalty for Julius and Ethel Rosenberg, convicted of giving atomic secrets to the Soviet Union — a charge the film shows was untrue. They were executed as spies in 1953. 

Meeropol calls the story “an impressionistic biopic” that’s filtered through her own experience. The story veers between personal and archival footage as well as interviews with “Angels in America” playwright Tony Kushner and gossip columnist Cindy Adams, who not only divulges Cohn’s financial habits — he instructed underlings to never pay his bills — but dishes on his relationship with Barbara Walters, whom he met in college.

As the documentary opens, we’re introduced to the director’s father, Michael Meeropol, telling young Ivy via home movies the story of what Cohn did to their family. (Meeropol had previously narrated her grandparents’ story in her 2004 documentary “Heir to an Execution,” which also included her father.) 

Editor Adam Kurnitz (Jim Jarmusch’s “Gimme Danger”), who took over for Anne Alvergue after she was unable to complete “Bully. Coward. Victim.” due to scheduling conflicts, points out that Meeropol easily could have eviscerated Cohn but chose to explore what motivates him. That Cohn was Jewish, like the Rosenbergs, and a closeted homosexual were part of the self-loathing that the film shows drove him. 

The documentary needed to “feel like a roller coaster,” says Kurnitz, frenetic when showing Cohn, whether in LGBT haven Provincetown, Mass., or tracing his beginnings as a law student at Columbia, or telling of his relationship with Walters or his mentorship of Donald Trump, including a deal Cohn brokered with a building company run by the mob in 1981 that allowed Trump Tower to be built during a cement workers union strike. “In this era of Trump, it seemed timely,” Meeropol says. 

In contrast, the scenes with Meeropol’s father were somber. “The pace would drop,” Kurnitz explains, as the doc shows the effect of Cohn’s actions on the family.

While the picture strives to explains Cohn’s behavior, Kurnitz cautions, “You didn’t want to represent him as someone you wanted to emulate.” So when we see Cohn at his happiest, in Provincetown in the ’70s surrounded by young blond men, there was a counterweight. “We showed those moments from [the perspective of John Waters], who was disgusted by Cohn’s presence there,” Kurnitz says.

The most striking image is perhaps the scene when the Meeropols, father and daughter, recall visiting the AIDS Memorial Quilt and witnessing Cohn’s panel (he died from AIDS-related complications in 1986). “Seeing that really stayed with me,” says Ivy Meeropol, “and it’s where I remember being truly fascinated by this man who haunted me and my family our whole lives.”