"I got bullied at primary school," Ritchard Gale told the Seven Network last night.
Ritchard, a Year Seven student, is depicted as the bully in the video, throwing a punch at Casey, who then body-slams him.
"I always used to get teased and I just snap back at that now," Ritchard said.
The Chifley College student also says that Casey in fact had bullied him prior to the altercation and threw the first punch.
"He abused me first ... he was like 'get to class, you idiot', all that sort of stuff," Ritchard said.
Peter Gale, the single father who is raising Ritchard, said he was worried about how the attention is affecting his son.
"(It has been) very hard, unbelievable," Mr Gale said.
Ritchard, who has been dubbed "Ritchard the Rat" on some online forums, said he was not really sorry about teasing Casey because, he claimed, the older boy started it.
Ritchard's mother Tina Gale said she was shocked at the video showing Casey picking up her son and throwing him down onto the ground.
"My son could have been a paraplegic out of it for starters," she said.
Meanwhile Casey Heynes's father says he does not think it's safe for Casey to return to Chifley College.
"That is the attitude I got, you know, he has to learn to live with it. You know, be a man, man-up, whatever," Colin Heynes told the Nine Network.
"He is not going back there ... it is not a safe place for him," he said.
Casey said that he wouldn't accept an apology from Ritchard as "it's just going to happen again".
"It doesn't really mean anything and he might just get his friends on me," he said.
Casey also said that his school had suspended someone who had bullied him in the past but that the bullies just come back and do it again.
He said he was bullied since he was in second grade, with children going as far as duct-taping him to a pole and teasing him about his weight.
On the now famous video Casey can be seen advancing towards the smaller boy, Ritchard, who repeatedly had hit him, with Casey picking him up and throwing him onto concrete ground.
The action has seen Casey dubbed "Casey The Punisher", or "Zangief" - the name of a fictional wrestler in a video game.
Ritchard sustained only a grazed knee in the incident.
