At least five people were killed in two gunfire incidents in the US state of Louisiana, police said, adding a manhunt was happening to arrest the suspect.

Dakota Theriot, 21, is accused of killing his parents– Elizabeth and Keith Theriot, both 50– in the town of Gonzalez in Ascension and three more people in Livingston.

"This is presumably one of the most horrible domestic violence incidents I've seen in quite a while," said Ascension Parish Sheriff Bobby Weber on Saturday.

The suspect has been charged with two counts of first-degree murder, illegal use of weapons and home attack, Mr Weber told the media.

Before killing his parents, Dakota Theriot murdered Billy Ernest, 43, Summer Ernest, 20, and 17-year-old Tanner Ernest on Saturday morning.

According to Mr Weber, the suspect's parents were alive when deputies arrived at their home later on Saturday and recognized their son as the gunman in the Livingston killings.

"We don't know what kind of possessions he has or how far he can run. But we don't think he has great means and a lot of resources," CNN quoted the Sheriff as saying.

Investigators were annoying to decide the motive behind the shootings. Mr Weber said detectives have not been able to talk anyone who knows the suspect well.