A Louisiana man is accused of emerging from a room in a mask and fatally stabbing his girlfriend, his girlfriend’s 15-year-old sister and injuring his own siblings during a family gathering, according to authorities.

Oscar Urias, 23, was with his girlfriend, Elizabeth Tornabene, 31, and her sister in their shared LaPlace home Sunday afternoon, joined by his 15-year-old brother and his 17-year-old sister visiting from Baton Rouge, the St. John the Baptist Parish Sheriff’s Office said.

The group had been talking in the living room when Urias and Tornabene went into a bedroom. Urias left the bedroom wearing a mask, armed with two “machete-style” knives, according to Sheriff Mike Tregre.

He was accused of stabbing Tornabene to death and wounding his own sister, officials said.

Urias then chased his brother and Tornabene’s sister as they ran from the home, eventually catching the girl inside a garage down the road where he fatally stabbed her, investigators said.

Deputies found Urias there and ordered him to drop the knives. He was taken into custody.

Urias’ sister was in serious condition at a hospital Monday. His brother was also wounded during the attacks and was treated and released Sunday, the sheriff’s office said.

The teenagers were not immediately identified. Authorities did not comment on what may have prompted the attacks.

Urias was charged with two counts of first-degree murder and two counts of attempted first-degree murder, news outlets reported. He was being held without bond Monday. It was not clear whether he had an attorney who could comment for him.