A woman thought to be his mother was weeping hysterically.
Meads said it was a traumatic incident to witness.
A St John spokeswoman said the child had been taken to Middlemore Hospital in a critical condition.
A police spokeswoman said WorkSafe would be leading an investigating into what happened.
Detective Gareth Brown at the Harry Beaumont Entrance to the Auckland Botanic Gardens where a 7-year-old boy was crushed by a gate. Photo / Steven McNicholl
Detective Gareth Brown said the boy's family was being supported at Middlemore Hospital.
"The boy has been playing on the gate when a car has come up and hit the sensor and the gate has opened.
"Unfortunately, the boy has been crushed,'' Brown said.
Police are helping the family, but there were language barriers, he said.