MONTREAL—A teenager was charged Tuesday with the premeditated murder of his little sister.

Eighteen-year-old Maor Attar was arraigned on a first-degree murder charge, but was unable to appear before a judge because he was in hospital with unspecified injuries.

He was arraigned by telephone and will remain detained until his next court appearance Sept. 8.

Attar pleaded not guilty.

His 14-year-old sister was found stabbed to death in the family home, in the tranquil Montreal suburb of Cote St-Luc, Que.

Their mother made the grisly discovery upon returning home Monday around dinner time.

The girl was pronounced dead at the scene.

Attar was picked up a few blocks away, several hours later, and was questioned overnight by police.

Police initially described him as an important witness before classifying him as a suspect on Tuesday.

It’s unclear how long Attar will be in hospital, where he is being kept under surveillance.

“He has some injuries, but I cannot say more about that,” said Crown prosecutor Veronique Michaud.

She confirmed the connection between the suspect and victim.

“He is the brother,” Michaud said.