It was fitting that a memorial service held Saturday for computer freedom activist Aaron Swartz, who killed himself on January 11 as he faced hacking charges, was open to all.

In a spacious meeting room in the heart of New York's East Village neighbourhood, friends, fellow activists and supporters of 26-year-old Swartz gathered to recount fond memories mixed with angry calls for justice and a continuation of the fights that Swartz dedicated his life to.

Swartz's girlfriend, Taren Stinebrickner-Kauffman, was firm in her belief that Swartz's death had been caused by a prosecution system that had threatened him with up to 30 years in jail for hacking an online collection of academic journals linked to MIT with the intent of releasing millions of research papers on to the internet.

She said the prospect of a trial had dominated their life together and that prosecutors in the case should be held accountable for a tragedy that has shocked the tech community worldwide. "He faced a deeply dysfunctional criminal justice system," she said, and blamed a recent delay as a final straw. "He was so scared, so desperate and so tormented, and more than anything else just so weary, he could not take it another day," she said.

Stinebrickner-Kauffmann asked the packed crowd of several hundred inside the famed Cooper Union building's Great Hall – a scene of major civil rights and anti-slavery speeches in the past – to fight on for internet freedom and win justice for Swartz. Her anger was matched by that of Roy Singham, a close collaborator with Swartz who founded the Freedom to Connect initiative.

In a fiery and emotional speech that earned a rousing standing ovation, Singham slammed the case against Swartz. "This was not suicide. It was murder by intimidation, bullying and torment," he said. "We must demand accountability for those who tormented Aaron." He cast Swartz as the latest in a long line of heroic activists trying to change a powerful and entrenched system. "He was, in my humble opinion, one of the true extraordinary revolutionaries that this country has produced," he said.

The actions that brought the case against Swartz were just part of a young life spent using his undoubted computer genius in the cause of internet freedom and trying to make as much information accessible to all as possible. He helped build the Reddit online community and had been an instrumental voice in defeating legislative efforts aimed at extending control over the internet.

But Swartz was also troubled by a long struggle with depressive moods. The US attorney for Massachusetts, Carmen Ortiz, who brought the case, has disputed claims that her office was too zealous. "This office's conduct was appropriate in bringing and handling this case. The career prosecutors handling this matter took on the difficult task of enforcing a law they had taken an oath to uphold, and did so reasonably," she said in a statement last week. It has also emerged that Swartz had been offered a plea bargain for a six-month sentence.

But during the moving memorial service, during which numerous speakers paid tribute to their friend and a video of a speech by Swartz was played, there was also a strong focus on the happy side of Swartz's life. Amid much laughter, a picture emerged of an intensely driven young man who had a playful side that won immense loyalty from friends and activists all over the world.

"Aaron would have loved to have been here," Stinebrickner-Kaufmann said. His longtime friend Ben Wikler paid tribute to Swartz's personality. "What I found incredible about Aaron was not only his dedication and his brilliance, but also how much fun he was," he said.

Another speaker, Holden Karnofksy, who heads the GiveWell charity industry group, remembered long walks through Brooklyn's streets with Swartz intensely debating everything from Victorian sexuality to the reliability of GDO figures.

But perhaps the most poignant vignette, especially in the wake of the outpouring of global emotion among hackers and internet professionals, came from journalist Quinn Norton, who had been a close confidant of Swartz's. It seemed to symbolise the link between his private and public lives. She described a camping trip in northern California in which the two had tried and failed to light a camp fire in the face of driving rain. But, upon later returning to the pile of wood they thought their sparks had failed to ignite, they discovered it had become a roaring blaze. Fighting back the tears, she described the scene. "It was strong enough to stay lit in the rain," she said.