"I heard him (the 12-year-old) yelling out and I realised straight away what had happened," Kemp said.
"The boy wasn't breathing and there was no pulse so I started doing the breaths and compressions and he started coming around."
Last night, the teenager was in a stable condition in Hawkes Bay Hospital, spokeswoman Anna Kirk said.
The Flaxmere community was already reeling from the sudden deaths of two other Flaxmere College students.
Fifteen-year-old Jahnaya "Naya" Staples died on November 4 and her friend Ebonie McKenzie died five days later - the day after Naya's funeral.
Both Year 11 girls were about to sit their Level 1 NCEA exams.
It is understood the two girls were friends with the 16-year-old boy, another Flaxmere College student.
Kemp said Karlos, who attends Irongate Primary School, should be commended for his quick action.
Karlos' mother, Neralee Edlin, said she was incredibly thankful her son found the teenager.
"He is so proud of himself, he feels he has done something really good, he has saved someone."
The 16-year-old was treated by emergency staff at the scene and then taken to hospital.
Kemp said he was comforted to hear the boy was stable.
Kemp met Karlos yesterday morning to have a chat and offer support.
The 12-year-old told him that he and two younger boys who had been with him hadn't slept much "and I told them I hadn't either".
"They did an amazing job getting help like they did.
"It was a pretty terrible thing for them to go through so I am hoping Victim Support will visit them soon."
Parents of students at Flaxmere College have been urged to watch their teenagers, and the Ministry of Education has confirmed it is providing assistance to the school.
A board of trustees member said the students had asked for an assembly involving the whole school to discuss their feelings and support each other.
"There needs to be something for these kids. We need to start talking more about how they are feeling and what we can do to help them."
Where to get help
• Youth services: (06) 3555 906
• Youthline: 0800 376 633
• Kidsline: 0800 543 754 (4pm to 6pm weekdays)
• Whatsup: 0800 942 8787 (noon to midnight)
• The Word
• Depression helpline: 0800 111 757 (24-hour service)
• Rainbow Youth: (09) 376 4155
• CASPER Suicide Prevention
If it is an emergency and you feel like you or someone else is at risk, call 111.
