Gene Hackman's costar Gary Sinise says star was living 'quiet life' outside Hollywood before mysterious death

Gary Sinise is just as shocked as the rest of the world after learning about the deaths of his former co-star Gene Hackman, Hackman's wife Betsy and their dog.

Sinise, who worked with Hackman in the 1995 film "The Quick and the Dead," told Fox News Digital he woke up early on Thursday and immediately saw the news of Hackman's death. The "CSI: NY" star had several questions.

"He's 95 years old, but his wife was in her 60s. So, like, what's going on there? You know, did something happen and was he not doing well?" Sinise wondered.

The Santa Fe County Sheriff's Department revealed autopsies were completed on both Hackman and his wife. No external trauma was seen on either the actor or his musician wife. Authorities continue to investigate the couple's deaths as official results of the autopsy and toxicology reports are still pending.

Sinise shared that he didn't stay in touch with Hackman after his retirement, but was aware of his "quiet life" in New Mexico with his wife. 

WATCH: GARY SINISE SAYS GENE HACKMAN WAS LIVING A 'QUIET LIFE' OUTSIDE OF HOLLYWOOD BEFORE HIS DEATH

"I know once he retired to New Mexico, he was retired. He did not want to come back and get any awards or, you know, go to any Hollywood events or anything like that. He was done and he was moving on from that part of his life," Sinise told Fox News Digital.

"I think he was painting. He was doing a lot of that and living a quiet life in New Mexico."

Sinise said Hackman has always been one of his role models.

"I just loved his approach. I loved his persona. I loved everything about him. And as time would go on, it was just like Gene never, ever failed. He could be in a movie that might be less successful than the one previous or whatever. But Gene Hackman was always outstanding," he said.

"I mean, he just never phoned it in. He was just a really fine actor to model after. I just wanted to be like Gene Hackman, you know, not that I ever turned out to be like Gene Hackman, but I had something to aspire to back then, and he was among my very favorites."

WATCH: GARY SINISE SAYS GENE HACKMAN WAS ONE OF HIS BIGGEST INSPIRATIONS

Sinise, who is an executive producer on the movie, said Rademacher decided to reunite with his brothers 10 years after his first documentary film, "Brothers At War," debuted.

Sinise told Fox News Digital that his foundation wants to help as many service members as possible through the production of this documentary.

"Soldiers and service members coming back from war and having a difficult time, it can be very hard. And we all know the difficulties that we've had with suicide in the military and all of that. We want to provide as many healing opportunities and healing services, of the Gary Sinise Foundation, for our service members as possible," he said.

WATCH: GARY SINISE HOPES VETERANS SEE HIS NEW MOVIE, 'BROTHERS AFTER WAR'

"Brothers After War" is in theaters now.

Fox News Digital's Stephanie Giang-Paunon contributed to this report.