Oklahoma

Officers confirmed that the suspected shooter, who was armed with a rifle and a handgun, was also dead.

Police arrived at the scene on Wednesday afternoon at St Francis Hospital in three minutes - which they say ensured the death toll wasn't higher.

Multiple injuries had also been confirmed, officials added.

Speaking at a press conference on Wednesday, Deputy Police Chief Eric Dalgleish said: "Right now we have four civilians that are dead, and one shooter that is dead."

Trisha O’Quinn remembers the day she and her grandmother came across the frantic couple, Jenni and Eric Easter, who were fishing on her family’s pond.

“We were going to ask them to leave when we noticed they were frantic and they said they were looking for her ring that fell off in the water. We helped them look for a long time with no luck and took down their name and number,” O’Quinn, 22, of Sayre, Oklahoma, said in an email to ABC News.

"They were dressed in black, all had masks on, and all had gloves on," Deputy Nick Mahoney told reporters.

The intruders - who police say were armed with brass knuckles and a knife - were shot by a 23-year-old man in an act of "self-defence", officers said.

The son may not face charges due to so-called stand your ground laws.

"This may be a case of 'stand-your-ground,' however, it's still too early to say for sure, and we're still looking into all aspects of this," Mr Mahoney told local media.