Answer by taking a quote from the following article:

John Bruce "Jack" Thompson (born July 25, 1951) is an American activist and disbarred attorney, based in Coral Gables, Florida. Thompson is known for his role as an anti-video-game activist, particularly against violence and sex in video games. During his time as an attorney, Thompson focused his legal efforts against what he perceives as obscenity in modern culture. This included rap music, broadcasts by shock jock Howard Stern, the content of computer and video games and their alleged effects on children.

Thompson was involved in a similar suit in Alabama in 2005 on behalf of the families of police personnel killed by Devin Moore, a teenager who was reportedly a compulsive Grand Theft Auto player. The lawyer's participation in the case, however, ran into a dispute over his pro hac vice, or temporary, admission to practice in that state. The opposing attorneys sought removal of the privilege by arguing that Thompson's conduct was unethical and claiming that he had threatened and harassed them in letters and emails. The judge added that Thompson had violated his gag order during Moore's criminal trial. Thompson tried to withdraw from the case, but his request was denied by the judge, who went ahead and revoked Thompson's temporary admission to the state bar.  For his part, Thompson said he thought the judge was trying to protect Moore's criminal conviction at any cost. He also complained about the judge's ethics, saying a local attorney who claimed to have influence on the judge had assured him the case would be dismissed unless the attorney was on Thompson's team, and also claimed that Rockstar Entertainment and Take Two Interactive posted slanderous comments about him on their website.  In the aftermath of this lawsuit, Thompson lobbied Alabama attorney general Troy King to file a civil suit and call on retailers not to sell "cop-killing games". After the slaying of another police officer in Gassville, Arkansas by Jacob D. Robida, an 18-year-old fugitive, Thompson again raised the possibility of a connection to Grand Theft Auto, but investigators found no evidence that video games were involved.

Was he successful in his efforts?
by Jacob D. Robida, an 18-year-old fugitive, Thompson again raised the possibility of a connection to Grand Theft Auto, but investigators found no evidence that video games were involved.