Robin Williams' suicide was a spontaneous act and was not planned out beforehand, according to a source close to the actor.

A confidante of Williams said they had a conversation with the comic a day before his death in which the two spoke about several upcoming projects.

The unnamed source said Williams had been 'completely engaged in the conversation' and was asking a lot of questions about the deals.

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Robin Williams suicide was spontaneous according to a confidante who says the pair discussed future projects the day before the comic actor was found dead

Speaking to TMZ, the source said: 'He [Robin] was unhappy which he often was, but it was nothing unusual... he lived in a dark place.'

Williams' family believe that whatever caused him to commit suicide happened shortly before he hanged himself at his California home, the website reports.

Since the actor was found dead a week ago today, several theories have surfaced as to why he might have taken his own life.

The actor Rob Schneider, who was a long-term friend of Williams, said he believed the actor's suicide was brought on in part because of new medication he was taking to combat the onset of Parkinson's disease.

Schneider tweeted: ‘Now that we can talk about it #Robin Williams was on a drug treating the symptoms of Parkinson’s. One of the side effects is suicide.’

The unnamed source said Williams had been 'completely engaged in the conversation' and was asking a lot of questions, indicating that he had not planned to kill himself

Experts say Parkinson’s disease can make symptoms of depression worse.

America’s National Institute of Mental Health says on its website that people struggling with depression and Parkinson’s ‘suffer higher levels of anxiety and more problems with concentration’ than those suffering from only one of the ailments.

Dr Jeff Bronstein, neurologist specialising in Parkinson’s, said: ‘Obviously getting the diagnosis can make people depressed but we also know there is a much higher incidence of depression even before the disease is recognised. We think it’s one of the early symptoms.’

However, a spokesman for Samaritans said: 'There is no simple explanation for why someone chooses to die by suicide, it is rarely due to one particular factor.

'Mental health problems are often a risk factor, as well as feelings of desperation and helplessness.

'We know that when a person is in crisis, they feel trapped in their situation with no way out, and that the future holds nothing good for them. They may not be able to see beyond their situation and truly believe that suicide is the only option for them.'

It is believed that family members paid tribute to the actor at a private memorial service this weekend organised by his widow, Susan Schneider - who is not related to Rob Schneider.

According to E! News, close friends and family arrived at the service in Tiburon, California, early on Saturday to pay their respects.