This weekend, someone writing on behalf of ISIS threatened Twitter co-founder Jack Dorsey and all Twitter employees, calling on supporters to not “allow any one of the atheists to survive.”

A post claiming to be in response to Twitter’s “campaign to delete accounts” specifically addresses Dorsey, who appears with superimposed crosshairs over his face.

“You started this failed war,” the ISIS post says. “We told you from the beginning it’s not your war, but you didn’t get it and kept closing our accounts on Twitter, but we always come back,” reads the message. “But when our lions [brave men] come and take your breath, you will never come back to life.”

It’s Twitter’s policy to suspend accounts that promote ISIS activity.

The post calls on ISIS supporters across the world to target Twitter and its employees.

“For the ‘individual jihadi’ all over the world, target the Twitter company and its interests in any place, people, and buildings, and don’t allow any one of the atheists to survive,” it says.

“Our security team is investigating the veracity of these threats with relevant law enforcement officials,” a Twitter spokesperson told BuzzFeed.

This isn’t the first time Twitter employees have been targeted by ISIS. CEO Dick Costolo revealed last year that he and other employees had received death threats.