American novelist Stephen King has hit out at the “proudly closed minds” on gun control in America following the murder of nine black churchgoers in Charleston, South Carolina this week.

Six women and three men were killed in the historic Emanuel African Methodist Episcopal church on Wednesday, with suspect Dylann Roof, a white 21-year-old who acquaintances have said had been “planning something like that for six months,” now in custody. According to Roof’s uncle, Carson Cowles, the 21-year-old, whom a Facebook picture has shown wearing a jacket bearing the flags of the former white-supremacist regimes of South Africa and Rhodesia, had been given the gun for his 21st birthday.

King wrote an essay on guns shortly after the 2013 shooting at Sandy Hook elementary school, Connecticut, which left 26 people dead. In it he called for a ban on automatic and semi-automatic weapons, calling them “weapons of mass destruction”, which “when lunatics want to make war on the unarmed and unprepared, these are the weapons they use”.

Until responsible gun owners support responsible gun control laws, innocent blood will continue to flow. How many times must we see this? — Stephen King (@StephenKing) June 18, 2015

On Thursday, King made the case for gun control once more, arguing on Twitter: “Until responsible gun owners support responsible gun control laws, innocent blood will continue to flow. How many times must we see this?”

There are “too many closed minds on gun control. Worse, far too many PROUDLY closed minds”, he added, and that “meanwhile, the American shooting gallery remains open”.

“According to Bloomberg Business, gun deaths will exceed traffic fatalities in America this year. Can’t put a seatbelt on a semi-automatic,” wrote the bestselling novelist, who is followed by almost three-quarters of a million people on Twitter.

King withdrew his own novel Rage, about a high-school shooting, following the 1996 murder in a Washington school of a teacher and two students by Barry Loukaitis. Loukaitis quoted a line from Rage: “This sure beats algebra, doesn’t it?” following the murders. A year later, Michael Carneal, who had a copy of Rage in his locker, would kill three people in a Kentucky high school.

“That was enough for me. I asked my publishers to pull the novel,” wrote King in his 2013 essay. “I didn’t pull Rage from publication because the law demanded it; I was protected under the First Amendment, and the law couldn’t demand it. I pulled it because in my judgment it might be hurting people, and that made it the responsible thing to do.

“Assault weapons will remain readily available to crazy people until the powerful pro-gun forces in this country decide to do a similar turnaround.”