"Ripped off my belt, said, 'Hey, this is going to hurt,’" Bitopoulos said.
He wrapped the man's leg in the tourniquet, called for help from nearby and minutes later, police arrived.
The man, later identified as Wagner Macedo, was rushed to Mass General Hospital. His left leg was amputated, said his son, Matheos Macedo.
"He bled a lot, and he had a bunch of transfusions. That's why I think Joe actually saved his life because he lost so much blood," Matheos Macedo said.
Matheos said his father is "OK. He's doing much better. He's a lot less groggy. He's happy my mom was there."
As a person of faith, Wagner knows who he wants to thank first and foremost, his son said.
"His first word when he woke up was ‘Jesus,’" his son said.
Then, comes Joe Bitopoulos.
'We think someone put him there for a reason," Matheos Macedo said.
The Macedos have been in contact with Joe, thanking him for being a Good Samaritan and saving Wagner.
While they call Bitopoulos a hero, he won't take the title. He said first responders and people like fallen Worcester firefighter Christopher Roy are the true heroes.
He hopes to meet with Wagner in the coming days.