There are a lot of ways to interpret “I am Groot,” but there’s no question that Guardians of the Galaxy director James Gunn has the definitive translations for each of the sentient tree-being’s phrases.

While Gunn isn’t going around translating every single phrase that Groot utters (we can usually get the gist), there is one line of Groot dialogue in Avengers: Infinity War that Gunn is open to sharing with us. And it may emotionally wreck you.

Major spoilers for Avengers: Infinity War follow.

As we saw at the end of Avengers: Infinity War, virtually the entire Guardians of the Galaxy team — apart from Nebula and Rocket — dissolved into dust after the snap heard around the universe. Most of them disappear with no more than a baffled or frightened look on their face, but a few of them managed to eke out a few last words. And one of those few who were able to speak before they disappeared into the void was Groot (Vin Diesel).

The notoriously stoic — though, now in his teenage years, just plain petulant — tree-being looks at Rocket Raccoon (Bradley Cooper) as he fades into dust, saying one last “I am Groot.”

What did that last “I am Groot” mean? The movie never gives us the answer, though the moment is so loaded with emotion that you can make your guesses. But the real answer is even more emotionally devastating than we thought. In response to a question on Twitter, Gunn revealed what Groot’s final line in Infinity War meant.

SPOILER…

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“Dad” — James Gunn (@JamesGunn) May 6, 2018

Yeah, we didn’t mean to spend Monday morning crying either, but here we are.

Groot called Rocket Raccoon “dad,” which makes the entire situation so much sadder. This version of Groot is still a kid, more or less, and he’s just confused as to why he and everybody else he loves is suddenly disappearing. If he had been paying attention to the everything going on around him instead of playing his video game, he may have been less confused, but bygones.

Yes, Rocket is essentially Groot’s surrogate father now, which ties into the Guardians’ dynamic of being a found family. You could probably extend Groot’s final line to the rest of the Guardians, who have tenderly raised Groot up from a tiny sapling. It’s certainly worlds away from Groot’s initial role as the stoic strong man of the group in the first Guardians of the Galaxy, but I wouldn’t have it any other way.

Avengers: Infinity War is currently playing in theaters.