Actor Sylvester Stallone portrays Rocky Balboa in a scene with his real life son, Sage Stallone, who portrays Rocky Balboa Jr., in the 1990 film "Rocky V" in this undated publicity photograph released to Reuters on July 14, 2012. Aspiring actor and filmmaker Sage Stallone, 36, was found dead on July 13, 2012 at his home in Hollywood, authorities and his attorney said.

A grieving Sylvester Stallone led mourners on Saturday at the private memorial for his son Sage, who died of a suspected drug overdose at the age of 36, last week.

The 66-year-old actor had his eyes shielded with sunglasses as he was joined by close family and friends for the service, held at St. Martin of Tours Catholic Church in Brentwood, Los Angeles.

Dressed in a black suit, a black tie and a white shirt, the actor was clearly devastated.

Following the service, the actor was seen watching his son’s casket being taken away by a hearse.

The hearse was then reportedly driven to Westwood Village Memorial Park Cemetery in Los Angeles, where Sage will be buried and finally laid to rest.

Sylvester’s ex-wife and Sage’s mother Sasha Czack, his current wife Jennifer Flavin, younger brother Frank and longtime friend and attorney Marty Singer were also in attendance at the funeral.

The star also received support from fans, who were seen holding up placards with pictures of the actor and his son from across the street.

Details of Sage’s funeral emerged earlier last week.

A source told RadarOnline.com: “Sage will be buried on Saturday. His body was picked up from the coroner by a mortuary that is based in Westwood earlier last week.

“The funeral will be private and it will be family and friends only and will be celebration of his life.”

Sage was found dead in his home with bottles of pills scattered all over his room, the LA County Coroner reported.

Toxicology results are expected within four to six weeks.

Hollywood star Stallone, who is said to be grief stricken by Sage’s death, released an emotional statement earlier last week, talking about his “agonising” loss.

He said: “When a parent loses a child there is no greater pain... This agonising loss will be felt for the rest of our lives.

“Sage was our first child and the centre of our universe and I am humbly begging for all to have my son’s memory in full left in peace.”

His funeral today comes after claims law enforcement sources revealed that authorities investigating the death of Sage believe he was a drug dealer.

Insiders apparently told TMZ.com that it is thought that a “likely scenario” is Sage was dealing Hydrocodone — more commonly known as Vicodin — but not an addict himself.

A key factor in this theory is said to be the late actor’s weight.

At 85.28 kilograms and 1.73 meters, Sage didn’t have the thin frame which is usually a trait of addicts.

TMZ was reportedly told: “He was pudgy, and drug addicts are almost always rail thin.”

The website’s source claimed that no Hydrocodone tablets were found in Sage’s house, but that there were over 60 gigantic empty prescription bottles.

Each of these would have held 500 pills, meaning that Sage would have had over 30,000.

LAPD detectives and LA County Coroner investigators will apparently use batch numbers and serial numbers to track down the bottles, but it is thought highly probably that they were shipped from abroad.

The bags of white powder found in the room where Sage died have not yet been tested, but it is said to be likely that they contained Hydrocodone.

Meanwhile a close friend of Sylvester’s late son has come forward to say that Sage did not take his own life.

Stephen Wozniak claims that Sage had no intention of committing suicide, and had been making plans for the future with him shortly before his death.

He added: “I’m certain that this really horrible thing that happened was an accident. It could have been anything — but nothing like suicide. I knew him pretty well.

“I spoke to him a few weeks ago. We talked about resurrecting a film we worked on, other projects, talked about his girlfriend and time they’d spent together. We talked about my wedding and he seemed to be thinking about it.”

While Wozniak does believe that Sage suffered from depression, he is adamant that the actor and director did not react to the problem with substance abuse.

Last week it was claimed that Sage’s father, Sylvester, hired a private investigator to discover exactly what happened to his late son.

According to TMZ.com, the actor met with top P.I. Scott Ross in an effort to understand what led to the tragic death of Sage.

The website reported that Ross was called to Stallone’s home to discuss the investigation with the actor, his brother Frank and an LA County Coroner representative.

Ross was behind the probes into the Chris Brown/Rihanna battery case and Michael Jackson molestation case.

While it is widely believed that Sage overdosed on painkillers following dental surgery, Stallone wants to know if he was using drugs or drinking alcohol in the lead up to his death, it is claimed.

According to TMZ.com, Ross has a history of working with Stallone and is a trusted friend.

This week, Sage’s mother Sasha revealed her belief that he had accidentally overdosed on pain medication following extensive dental work.

In her first public comments on her son Sage’s death, Czak said she had begged him not to have so much dental work carried out in one day.

She said her son had five teeth extracted two weeks before he was found dead at his Hollywood home.

Czak, Stallone’s first wife, said she had warned her son about having so much dental work carried out in one sitting.

“I told him not to do that. I’ve heard about people dying having multiple procedures done to you mouth. Do not have more than one tooth [pulled],” she told the New York Post.

When asked if her son would be taking pain medication, she added: “Wouldn’t you be?”

Los Angeles coroner Ed Winter has denied reports that Sage was living in squalor when his body was found.

One report said he was surrounded by rubbish and cigarette butts and had become a recluse.

“Sage Stallone wasn’t living in squalor. His home wasn’t unordinarily messy. It seemed to be a typical male messiness. Mr Stallone did have a housekeeper,” Winter told website Radaronline.

Although foul play is not suspected, Los Angeles detectives are helping out in the investigation.

Sage’s lawyer has said he was planning to get married and was not depressed.