Who Stabbed DeLuca on 'Grey's Anatomy'? Fans Have Theories About His Attacker

WARNING: SPOILERS for Season 17 of Grey's Anatomy ahead.

Fans of Grey's Anatomy have watched Andrew DeLuca grow and evolve over seven seasons of the long-running ABC series. Tragically — just when it seemed like the general surgery attending finally had a handle on his bipolar disorder, and things were looking up for home all around — the beloved character was killed off.

Now, fans just really need to know: Who stabbed DeLuca?

On the Grey's Anatomy mid-season premiere on March 11, during a storyline that carried over from Station 19, DeLuca (Giacomo Gianniotti) and his sister Carina (Stefania Spampinato) followed a human trafficker known as "Opal."

DeLuca had previously suspected she was trafficking her "niece" — a patient named Cindy (viewers eventually learned her real name was Erin) — but since the general surgery attending was in the middle of a manic episode, no one believed him.

It turned out DeLuca was right about Opal and although the red-headed woman got away, Cindy/Erin was ultimately saved.

So when DeLuca again spotted the woman outside of Grey-Sloan Memorial Hospital, he knew he had to act quickly. "I let her out of the hospital once, I'm not doing it again," he told Carina.

Although Carina tried to talk him out of it, she ultimately decided to help her brother — if only to make sure he didn't do anything too dangerous. With Carina driving, the siblings followed Opal's vehicle and called Carina's girlfriend, Station 19 Captain Maya Bishop (Danielle Savre), for help.

Carina and DeLuca ended up following Opal onto a subway train as the Station 19 crew and other law enforcement officials arranged to meet them at an upcoming stop. Ultimately, Opal was intercepted and arrested. Shockingly, though, DeLuca was stabbed after he exited the train.

Here's the thing: We know it wasn't Opal who stabbed DeLuca. The attacker appears to have been the guy who "bumped into" DeLuca after he got off the train, but his identity wasn't immediately clear.

Many viewers think the person who stabbed DeLuca was actually Opal's partner, the guy with whom she spoke in an alley on her way to the subway station.

But there's another theory: What if the man who stabbed DeLuca had nothing to do with child trafficking?

Perhaps it was someone on the train who overheard DeLuca and Carina speaking in Italian. There were a couple of uncomfortable/rude passengers who either moved away from them or made a snide remark upon hearing the siblings speak to each other in the native language. So maybe DeLuca's stabbing was a completely unrelated hate crime.

Fan theories aside, Carina revealed during her last time ever talking with DeLuca (although she didn't know it at the time *SOB*), that both Opal and his attacker had been caught.

"You did it. It's over. They arrested the woman. They arrested the man that stabbed you. You saved so many children, Andrea," Carina said her brother in the hospital, after he regained consciousness following emergency surgery.

It looks like viewers will just have to wait and see who stabbed DeLuca; heartbreakingly, it won't change the fact that he died.

At least DeLuca knew he stopped the human trafficker ... and Carina got to see him one last time ... and Meredith had a chance to say goodbye on the beach. (Honestly, we're still processing his death and can't believe he's really gone.) RIP Andrew DeLuca.

Watch new episodes of Grey's Anatomy on Thursdays at 9 p.m. ET on ABC.