'Stranger Things' 4: Netflix adds graphic violence warning after Texas school shooting

Stranger Things cast
Stranger Things season four streams on Netflix from Friday, carrying a content warning in the US. (Netflix)

Stranger Things series four began streaming on Netflix on Friday carrying a new graphic violence warning for US viewers in the wake of the Texas primary school shooting.

The hit sci-fi series makes its highly-anticipated return in the same week as the horrifying shooting at Robb Elementary School in Uvalde, Texas on Tuesday, which left 21 people dead — including 19 children and two teachers.

Read more: Stranger Things four cast - who's who

Netflix viewers in the US will see a warning card come up if they select the programme that refers to a violent scene at the beginning of episode one.

It will say: "We filmed this season of Stranger Things a year ago. But given the recent tragic shooting at a school in Texas, viewers may find the opening scene of episode 1 distressing. We are deeply saddened by this unspeakable violence, and our hearts go out to every family mourning a loved one."

Millie Bobby Brown as Eleven in a school classroom. (Netflix)
Millie Bobby Brown stars as Eleven. (Netflix)

The programme is set in a school in America, where a group of friends come into contact with a strange and violent presence after meeting an unusual new friend, Eleven, played by Millie Bobby Brown.

Eleven has supernatural powers but is in danger from dark forces in an alternate universe called The Upside Down that has at points claimed various other characters and terrorised the group with a monster called the Mind Flayer.

Read more: Stranger Things season three recap

Series four sees Eleven and the Byers family, who have taken her in since her adopted father Hopper was captured by the Russians last series, living in a new town, but the trailer shows that their old friends in Hawkins are in need of their help.

As the story centres on a group of school-age friends, many of the scenes take place at their school, but it has also been billed as the scariest season yet - which includes the opening moments.

The Stranger Things cast
The Stranger Things gang are facing terrifying new villains in season four. (Netflix)

The first episode of series four begins with a flashback to Eleven's past in the Hawkins lab, before she escaped to live with Hopper.

It shows a group of other super-powered children lying murdered on the floor of the lab and Eleven covered in blood, apparently responsible for their deaths.

The series description for US viewers will also include "Warning: Contains graphic violence involving children" and the tag "disturbing images" in its show rating advisories.

Stranger Things series four is currently streaming on Netflix.

Watch: See the trailer for Stranger Things season four