TORONTO, Ont. – The man accused in a deadly crossbow attack at Main Library Thursday afternoon is the victim’s son, police confirmed Friday.

The 24-year-old Ottawa man has been charged with first-degree murder in Thursday’s crossbow attack in Toronto that left his 52-year-old father, Si Cheng, dead.

“We know this was not a random attack but it was a targeted attack, and we’re still looking behind the motivation behind the killing,” said Toronto Police Constable Tony Vella.

“One of the major factors in this case is what sparked the shooting, and that’s still something that needs to be determined and we’re still looking at that,” he told 680News.

Zhou Fang stared straight ahead and spoke softly during a brief court appearance Friday. He remained quiet as he was returned to his cell, and will remain in custody until his next court appearance on December 8.

Police said Cheng, of Toronto, was pronounced dead at the scene after he was shot in the back with a crossbow inside the Main Street Library.

His murder was witnessed by dozens of people, including children, who were inside the building at the time.

Police said Fang reportedly entered the library, located near Gerrard Street East and Main Street, dressed in dark clothes around 4 p.m. Thursday and allegedly started firing a crossbow, hitting the victim. Fang then fled the library on foot and got into a U-Haul and was arrested minutes later in east-end Toronto.

Toronto Public Library officials issued a statement on Twitter saying their thoughts are with the families, adding all library staff are safe. The library remains closed indefinitely as detectives continue to comb the library for evidence.

A spokesperson said a security guard will be on-site to give employees peace of mind when the location does re-open.

Meanwhile, the Toronto Sun reported Friday that the victim’s ex wife had lived in constant fear of her former husband.

Court documents show that Cheng had two domestic violence convictions.