"I saw that the prisoner was standing so he wasn't shackled to the remaining prison guard and then in a split second I saw the prison guard go 'oh f...' and ran off.
"I never thought that he would actually get away."
Prison director for Rimutaka Prison Viv Whelan said Keepa, who was on remand for an alleged serious assault, "absconded from custodial staff" while attending a hospital appointment.
"Primary healthcare services are provided in prisons. Prisoners are escorted to local clinics or hospitals for assessment or treatment of more serious concerns," Whelan said.
"A full investigation will be carried out."
Keepa was last seen in Avalon near Kennedy Good Bridge and State Highway 2.
He is described as being 172cm tall, medium build, with distinctive tattoos on his neck.
Police confirmed this afternoon Keepa has not been found yet.
Police are searching for him but are asking that the public report any sightings of him or information on his whereabouts.
Keepa is not considered dangerous to the general public however he should not be approached and anyone who sees him should contact police on 111.
Alternatively information can be provided via Crimestoppers on 0800 555 111.
A Hutt Valley District Health Board spokeswoman yesterday said the DHB has "robust procedures" for managing patients who are in custody.
"A memorandum of understanding with Corrections and the New Zealand Police sets out exactly how prisoners are managed and is there to protect our staff, patients and members of the public. Safety is our highest priority.
"We have expressed concerns with Corrections about the incident. We wish to assure the public there is no further risk to patients or staff."
