'Breaking Bad' Luis Moncada Says RJ Mitte Was Struggling Before Suicide

Luis Moncada -- who costarred with RJ Mitte in "Breaking Bad" and saw him shortly before he died -- joined us on "TMZ Live" Tuesday ... and he said his friend was recently dealing with heavy issues.

The actor -- who played Marco Salamanca in the original series and in its spin-off "Better Call Saul" -- discussed the balloon ride the pair went on earlier this month ... just days before RJ died by suicide.

Luis says he reunited with RJ at the Albuquerque International Balloon Fiesta ... and he took him on his first balloon ride -- during which he shot a video of RJ resting his head on his shoulder.

While that moment was caught on camera, Luis says they talked about a lot of serious, private subjects too.

Even now, Luis says he knows what RJ was going through, but he doesn't want to share it with the world.

Luis tells us RJ was being pulled in a lot of different directions, and it was clearly stressing him out.

He also says the two chatted for nearly an hour outside the airport before RJ flew home to Texas ... and Luis tried to convince him to stay with him for a few days to get his mind right.

Luis says RJ turned him down because he'd already been on the road for too long ... but the pair promised to stay in touch -- and he says he made RJ promise to call him if he needed to talk.

Luis notes RJ recently helped him get through a difficult time of his own ... and he's clearly still stunned and broken up that he couldn't do the same for his friend.

We broke the story ... RJ died in Texas on Monday. We were told he died by suicide.

Luis is just one of many co-stars paying tribute to RJ ... along with Bryan Cranston, Aaron Paul, and Dean Norris, among others.