Drikus Van Der Merwe was part of the filming crew and said he was stood next to Carlos when he was attacked.
'He started chasing the boom swinger who joined our unit,' he added. 'The giraffe followed him but we didn't feel threatened because he just seemed to be inquisitive.
'We started shooting close ups of its body and its feet. Then while Carlos was looking through the camera eyepiece Gerald swung his neck and hit him against his head.
'It came out of nowhere and Carlos didn't even see it coming. He wasn't aware of the danger.'
The tragedy happened at the popular 1500-acre Glen Afric Country Lodge in Hartbeespoort which is 50 miles north the hospital he was flown to on Wednesday night.
Van Der Merwe said Carlos's body lay lifeless on the ground until the on-set paramedic arrived.
'I could see he was unconscious,' he said. 'There was blood coming out of his eyes and ears so I knew he had a severe head trauma. But I never thought he would die.
'Out of all the wild animals we have filmed I can't believe a giraffe killed Carlos. I suppose we get so used to filming animals that we become desensitised in a way.'
Moments before the attack, photographer Van Der Merwe took the final pictures of Carlos alive as he worked on rigging.
Owner of Glen Afric Country Lodge Richard Brooker yesterday told how he was killed.
He said: 'Carlos was standing in front of the giraffe, the animal spread its legs, bent its neck and swung its head at Carlos. It was a terrible accident and we are heartbroken.
'Gerald will remain at the lodge. He did nothing wrong.'
Carvalho won a number of awards since he began his career as a runner in 1992.
They included a Silver Lion at the Cannes Film Festival in 2003 for a public service announcement for Childline and a 2014 African Movie Academy Cinematography Award for his work on "The Forgotten Kingdom".
Adult male giraffes which stand 18 feet tall and weigh up to 1.2 tons fight with their heads in what is called necking to prove dominance and for the right to access to females.
As the video below shows it can be very violent and can result in serious death or injury.
Carlos had his skull crushed by the horns known as ossicones on the top of the giraffe's head .
The filmmakers Cape Town agent Sandi-Lee Slabbert said: 'The giraffe headbutted Carlos during filming and he was rushed to hospital but died that night from head injuries.
'He was an amazing, amazing man and fabulous to work with. Everyone loved him and loved working with him.
'He was very well known at Glen Afric where he filmed a lot. He is a very sad loss to everyone who knew him and the industry.'