The family of the actor who played in "Harry Potter and the Half-Blood Prince" and was killed on Saturday urged authorities to impose tougher penalties for youths who carry knives.

British actor Robert Knox was stabbed outside a bar on Saturday morning in a southwest London suburb after an argument with the one who killed him. The 18-year-old Briton died of his injuries. A 21-year-old is currently in police custody and suspected of murder.

Robert Knox played a student from Ravenclaw House at the Hogwarts School of Witchcraft and Wizardry in the sixth part of the "Harry Potter" series coming out in November. Media reports show that he had also signed to star in "Harry Potter and the Deathly Hallows."

"We are all shocked and saddened by this news and at this time our sympathies are with his
family," Warner Bros. Studio, the producer of the Harry Potter series, said in a statement.

According to police reports, Knox was stabbed when he intervened to protect his younger brother Jamie who was threatened by a man inside the bar. The man attacked the two brothers outside the bar. He had two knives at him according to The Times which quoted the police report.

Strangely, Colin Knox, the actor’s father, said the last conversations he had with his son was about knives and how dangerous they can be, The Times reported.

"With knives there are no winners and only losers,” said Mr Knox., who added that the high number of deaths through stabbing is a political issue and authorities should take measures.

Bronx was the fourteenth teenager who died of a violent death in London this year and the ninth to be killed through stabbing.

In a statement, Knox’s parents, Colin and Sally, described their son as a “kind and thoughtful” boy who always helped the others.

"The life and soul of the party, he was very outgoing loved sports and would always strike up conversation with people,” his parents added in the statement released on Sunday.