Iranian immigrant Shay Khatiri created an online fundraiser for the victims of Tree of Life*Or L’Simcha Synagogue in Pittsburgh after waking up on his Jewish friend’s couch to the heartbreaking news that 11 mostly elderly Jews were shot dead by an armed gunman who entered during weekly Shabbat services on Saturday. Six others were injured in the Oct. 27 attack.

“She told me what happened, and she was just broken,” Khatiri told CNN. “Seeing how upset she was, I wanted to donate to the congregation.”

“I thought to myself, I could donate $18 or $36—something like that. But that wouldn’t make a huge impact,” he said. “If I did something like this, maybe it could go viral.”

As of Monday afternoon, the 29-year-old graduate student’s certified GoFundMe campaign has raised $639,281 out of a $1 million goal.

In less than 48 hours, more than 11,000 donations have poured in. Half a million of the funds were raised by Sunday evening.