One of the many problems Bernie Sanders will have to deal with over the next few months of campaigning is the zealotry of his own supporters. Today CNN published a story suggesting Sanders followers are uniquely aggressive online often bullying those who fail to fall in line. It’s titled “The ‘swarm’: How a subset of Sanders supporters use hostile tactics to drown out critics.”

More than a dozen social media users spoke to CNN about their experiences with bullying by Sanders supporters. They described threats against family members, the creation of imposter accounts that resembled their own and what some described as being “swarmed,” where barrages of vitriol filled their Twitter feeds and inboxes for days after they posted something critical of Sanders. “I had never experienced that level of aggression before,” said Patty Kasbek, a veterinary technician in Oklahoma who said she criticizes President Donald Trump on Twitter more than any other political figure but said she faced the most hostility after she accused Sanders of being misogynistic. She said she received messages such as “STFU” and “eat this” poop emoji, among other insults. Two other targets said they were so tormented by the online attacks they faced following their public questioning or criticism of Sanders that they requested those specific circumstances not be reported for fear such harassment could start up again. Both said Sanders supporters exposed their addresses, shared their personal photos and spread information about their relatives and work colleagues.

Sanders had tried to discourage bullying tactics on a few occasions but critics note that Sanders also frequently strikes an angry pose online that amps up his followers: