A bisexual teenager who took his own life was the victim of years of bullying, according to his father.

Adam Kizer, 16, of Sonoma, California, passed away over the weekend after being taken off life support four days after hanging himself at his home.

The teenager had attempted suicide at times before, and also suffered from both depression and post-traumatic stress.

WARNING GRAPHIC IMAGES

Tragedy: Adam Kizer (left) took his own life after years of bullying. His father posted a photo of him at his wake saying his siblings wanted one last photo with their brother (right) and that he wanted people to see it online

Bullying: 'I don’t think the boy went a whole week without somebody messing with him,' said Adam's father William (above Adam and a friend at a high school dance)

'It’s the worst pain you can ever imagine,' Adam's father, William Kizer, told The Press Democrat.

The man also revealed that his son had been suffering since he was a boy due to constant bullying from other children, including once when some boys doused him in gasoline.

'They were going to light him on fire,'William said.

'Adam was able to get away.'

He also revealed that high school students were often telling his son that he should kill himself.

'I don’t think the boy went a whole week without somebody messing with him,' he said.

'They would tell him "You should kill yourself."'

There was also an incident in 2011 that led to Adam being expelled from the Adele Harrison Elementary School, and he then spent the next two years in a group home as part of the juvenile justice system.

He started high school soon after his return home, and six months ago came out as bisexual.

In memory: Friends remembered the young man at a memorial over the weekend (above)

Pain: 'He was my best friend. I still can’t believe he’s gone,' said Adam's father (memorial above)

Loss: 'It’s the worst pain you can ever imagine,' said Adam's father

His depression grew worse however according to his father, and in the weeks leading up to his death the young man made other attempts to take his own life.

He was found on May 26 after hanging himself, and put on life support as soon as he arrived at the hospital, but four days later he was dead.

'He was my best friend,' said his father.

'I still can’t believe he’s gone.'

William is blaming the school, the juvenile system and mental health officials for his son's death, and is considering taking legal action.

He also shared a photo of his son laid out at his wake on Facebook, writing; 'A father's worst deal has come true.

'I'm sorry if this bothers people but my kids want people to see them with there brother for the last time. Thank you everyone for your support love the Kize's.'

A GoFundMe page has also been set up for the family at this difficult time.

This money will go towards Adam's funeral service.