"Fast and Furious 7" is nearing completion, but new reports suggest that star Vin Diesel was not that easy to work with on set.

Rumors speculate that co-star- Paul Walker's death- really took a toll on Diesel. The actor paid tribute to his beloved co-star by posting a throwback photo of them on Facebook on Thursday.

The said photo was taken from the 2002 MTV Movie Awards. Diesel posted a long message with the photo saying:

"A song comes to mind... with this throwback pic....

"Has anybody here, seen my old friend Pablo... Can you tell me where he's gone... he helped a lot of people, but it seems the good die young, I just looked around and he was gone...

"Thank you all for being with us the whole way. Fast Family!" he wrote.

The Hollywood Reporter has also previously reported Diesel's odd behavior on the set of "Fast and Furious 7."

An insider told the magazine that there were days that Diesel would spend long times, even the whole day, alone in his trailer. And in one occasion, even called executives to ask "What the f*** am I doing here?"

People close to the "Fast and Furious 7" star think that it has really been hard for Diesel after Paul Walker's untimely death.

Diesel was always vocal about it, and would even share how uncomfortable it was having Walker digitally included in the new film.

"He always knew I would fight for him... whether it was to protect his deal or to protect his integrity... and he knew that if it made for a better film, I was going to do whatever it took... it is why together, we won best duo... twice, 12 years apart," Diesel wrote in a Facebook post.

"With our new ambitious vfx team, the whole cast and crew has had to adjust to this awkward and uncomfortable process of pixels over people. Aside from the obvious strains it places on the director, the challenge is not to allow it to compromise what makes the character so special," he added.

"Fast and Furious 7" starring Vin Diesel and featuring Paul Walker is slated for an April 10, 2015 release.