(Reuters) - A gunman in Arkansas who killed three people, including a 12-year-old girl, and wounded four others before taking his own life had been released recently from a mental health treatment hospital, police said on Sunday.

The suspect in the shooting rampage on Saturday afternoon, identified as Porfirio Hernandez, 40, was acquainted with his victims, Jonesboro Police Chief Mike Yates said at a press conference.

Hernandez entered a home near Jonesboro, about 130 miles northeast of Little Rock, armed with a .357 magnum handgun and opened fire, killing a 38-year-old man and a 12-year-old girl, Yates said. The girl's age was originally thought to be 13.

Four other people in the home were wounded, including boys aged 10 and 8 and two adults aged 43 and 36. The 10-year-old victim was upgraded to stable condition on Sunday, while the other three remained critical, police said.

A short distance from the home, a 31-year-old man was found shot and killed at his place of employment by the same gun, Yates said.

Hernandez was found in the driver's seat of a vehicle on a highway, dead of a gunshot wound.

The motive for the shooting spree was not yet clear. Hernandez was released from a mental health facility just days beforehand, and police were trying to determine how he obtained the gun, Yates said.

In Arkansas, gun possession is illegal for anyone who has been convicted of a felony or committed involuntarily to a mental institution.

(Reporting by Victoria Cavaliere; Editing by Colleen Jenkins and Marguerita Choy)