WILKES-BARRE, Pa. – A 14-year-old Pennsylvania boy was charged with barging into a neighbour’s house and stabbing a married couple and their teen daughter, killing the husband, in an attack whose motive remained unclear Tuesday.

Zachary Hockenberry was charged as an adult and jailed without bail following the attack Sunday at a home in Kingston Township, near Wilkes-Barre.

Police said Bobbi Jo Sinoracki was vacuuming when she felt like she was being punched in the back. Sinoracki turned around, saw Hockenberry holding a knife and realized she had been stabbed, according to court documents.

Police said Hockenberry then stabbed David Sinoracki in the chest. Hearing her mother’s screams, the couple’s 17-year-old daughter ran into the living room, tried helping her mother and was also stabbed in the chest.

Hockenberry’s father wound up in the home and restrained his son in a chair until police arrived, Luzerne County District Attorney Stefanie Salavantis said Tuesday.

Authorities said they do not know what spurred the attack. Kingston Township Police Chief Michael Moravec said Hockenberry had no apparent history with the family.

“Quite frankly, we’re at a loss as to what exactly the motive is going to be, ultimately, with this child,” Moravec said Tuesday.

Frank Nocito, the suspect’s lawyer, said he will try to postpone Hockenberry’s preliminary hearing, but he otherwise declined to comment.

David Sinoracki died at a hospital. Bobbi Jo Sinoracki was admitted with multiple stab wounds but is expected to recover. Their daughter was treated and released.