A British anti-gun violence charity has called on Valve to remove a "school shooting simulator" from the Steam store before it goes on sale next month.
The Infer Trust, which offers support and advice to those affected by gun violence, described the game as "horrendous".
"It is in very bad taste," a charity spokesperson told the BBC. "There have been 22 school shootings in the US since the beginning of this year.
"It is horrendous. Why would anybody think it's a good idea to market something violent like that, and be completely insensitive to the deaths of so many children?
"We're appalled that the game is being marketed."
However, the Russian developer refuted such accusations, saying the game "does not promote any sort of violence, especially any soft [sic] of a mass shooting", arguing that players can take on many different roles in the game.
The indie developer also suggested that titles like Hatred, Postal, and Carmageddon are much worse and have a more deliberate focus on mass murder.
Valve has attracted criticism for failing to take action, despite just last week warning developers of games with sexual elements to censor content or have their work removed from Steam.
GamesIndustry.biz has reached out to Valve for comment, and is awaiting response.