"I just think he loves her," Gyllenhaal's producer pal Ryan Kavanaugh told PEOPLE at the 23rd Annual "Salute to Youth" dinner in Los Angeles on Thursday.
Kavanaugh produced the actor's upcoming film, Brothers, which he calls a "passion project."
"[Jake] has obviously had his fair share of dating," Kavanaugh says of Gyllenhaal's romantic life. "I think eventually you come to a place where you know what you want and seeing what we saw on the set, he was certainly completely devoted to her and really loves her."
Over the course of the film, the producer really got to know Gyllenhaal, 27. "He's awesome," says Kavanaugh. "He's a true artist and a really good guy. We used to workout every morning before going on the set so he became a good friend, too."
Reporting by ALONDRA HERNANDEZ