"Police are still working to determine the circumstances surrounding the shooting."
Police are continuing to appeal for information to help identify those responsible.
Anyone with information is asked to contact police on 105 or online at www.police.govt.nz/use-105, using Update My Report and referencing the file number 220928/5363.
Information can also be provided anonymously via Crime Stoppers on 0800 555 111 or at www.crimestoppers-nz.org.
Police responded to the incident around 9.45pm.
The two young people and woman were outside the property at the time, and went to Gisborne Hospital with gunshot-related injuries.
A 12-year-old was "less seriously injured" and was discharged to her whānau, Tairāwhiti Area Commander Inspector Sam Aberahama said.
Another teenager was seriously injured and remains in hospital. The woman was "moderately injured" and remains in hospital.
"This behaviour is completely unacceptable and is incredibly concerning when young people are injured as a result," Aberahama said.
"There have been several high-profile firearms events in Gisborne this year in which women and children have been injured or killed as a result."