(CNN) Two teenagers have been charged with first degree murder, and two more were arrested Tuesday in connection with the stabbing of a 14-year-old boy outside a school in Ontario, Canada, police said.

Hamilton police identified the slain teenager as Devan Selvey, a student at Sir Winston Churchill Secondary School in Hamilton, about 50 miles west of Niagara Falls.

A 14-year-old boy and an 18-year-old boy were charged and appeared in court. On Tuesday morning, a 16-year-old boy and a 16-year-old girl were also arrested, police said.

The two 16-year-olds remain in custody as authorities investigate their involvement, Hamilton police said.

Police believe they've located the murder weapon after conducting a ground search of the homicide scene, Det. Sgt. Steve Bereziuk said in press conference.

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