“Grey’s Anatomy” will hit us where it hurts on Thursday when the ABC series returns with its Season 12 winter premiere episode, “The Sound of Silence.” Viewers will watch helplessly as Meredith (Ellen Pompeo) gets brutally attacked by a patient.

Audiences got a glimpse at the gut-wrenching scene in a sneak-peek clip from the forthcoming episode. But it wasn't disclosed why the patient went after the Grey Sloan surgeon … until now. A new promo video for episode 9 reveals what caused the patient to turn Meredith into a rag doll during the midseason premiere.

“The guy who did this, he was stable non-aggressive,” Ben (Jason George) says of the patient who attacked Mer. “He was a threat. I left him for five minutes and this happened.”

Owen (Kevin McKidd) chimes in, explaining that the patient was postictal. According to Epilepsy.com, postictal is a phase that occurs following a seizure. Others recover during this time, while some are left feeling confused, scared or anxious.

“Hyper-aggression can occur after a seizure,” Owen elaborates, revealing that their patient was someone whose postictal phase included feelings of hostility. Richard (James Pickens Jr.) adds that the incident occurred during a temporary fugue state, meaning that Meredith’s attacker won’t even remember laying a hand on her.

In the sneak-peek video it was revealed that Meredith is suffering from a long list of wounds, ranging from bruising on both her left chest and left knee to collapsed veins. And according to Pickens, it will be up to the surgeons of Grey Sloan Memorial Hospital to put their friend back together during the Season 12 winter premiere.

"[The attack] makes us realize how much of a family Seattle Grace really is and how in times of trauma and times of turmoil, how you come together for the common good. In this case, it's saving [Meredith's] life basically," the actor divulged during an interview with E! News.

Tune in to the chaos when “Grey’s Anatomy” returns on Thursday, Feb. 11, at 8 p.m. EST on ABC.