Leland Michael Foster, 27, was shot fatally in Oklahoma on Friday

A hero neighbor shot and killed a maniac with a knife who was trying to drown his own three-month-old twins.

Cash Freeman fired at Leland Michael Foster, 27, twice on Friday in Ada, Oklahoma, killing Foster while he was holding a mother at bay with a knife and trying to submerge the babies in the bathtub.

The infants, a boy and a girl who were born prematurely, have been treated and released from the hospital.

The horror scene unfolded around 12.30pm on Friday, when a frantic woman called police.

She said the father of her three-month-old twins had a knife and was trying to drown the babies, Ada Public Information Director Lisa Bratcher told theAda News.

The woman said that Foster had threatened to kill her, while dispatchers could hear struggles and screaming over the line, Bratcher said.

Police raced to the scene, but before they could get there, the homeowner's 12-year-old granddaughter went to the neighbor's house and pleaded for help.

Neighbor Cash Freeman, pictured with his wife, was alerted by a 12-year-old girl living in the house next door that Foster was trying to drown his own three-month-old infants

Neighbor Cash Freeman armed himself with a revolver and rushed to help.

When he entered the neighbor's home he found Foster holding the infants' mother at bay with a knife while actively trying to drown the twin babies in a bathtub, police said.

Freeman fired twice, killing Foster.

He was interviewed and released by cops at the scene, but prosecutors will review the circumstances to ensure that the shooting was justified.

Police confirmed that Foster was the father of the twins.

The infants were air-lifted to a hospital in Oklahoma City and released on Saturday.

Freeman armed himself with a revolver and shot Foster as the father tried to drown his infant twins. He was not arrested but prosecutors will review the shooting to ensure it was justified

The street where the incident took place is seen. The twins were air-lifted to a hospital in Oklahoma City and released on Saturday

'It’s awful because I’ve held the babies and, like, I’ve played with them and I just gave them clothes yesterday,' neighbor Summer Pierce told KFOR.

Foster has prior criminal charges for arson and domestic abuse by strangulation, according to court records.

In 2011, officers responding to Foster's home on a domestic abuse complaint found a pile of clothes burning on a mattress, and a bathtub filled with water and electronics including a computer and gaming system, NewsOK reported.