Seven Cambodian men were charged in court Sunday with involvement in the death of a 2-year-old Canadian boy during last week's takeover at an international school.

Four men accused of carrying out the attack on the school near northwestern Cambodia's Angkor Wat (search) temple complex were charged with premeditated murder, kidnapping, illegal detainment of persons for ransom and illegal use of a weapon, prosecutor Bou Bunhang said.

The charges carry penalties ranging from 15 years to life in prison.

Their three alleged accomplices — two private security guards and a man who sold the handgun used to kill the Canadian boy — were charged with conspiracy to commit premeditated murder, illegal detainment and illegal use of a weapon. One of the guards worked at the school.

Four men stormed Siem Reap International School on Thursday and held about 30 students and some teachers hostage for more than six hours.

Their alleged leader, Chea Sokhom (search), used the handgun, their only weapon, to shoot the Canadian boy in the head because he would not stop crying, according to police.

The crisis ended when police cornered the van in which the attackers tried to escape with several child hostages and a reported $30,000 ransom.

Ou Em, head of the serious crime division in Siem Reap province, said police Saturday arrested Un Nee, who allegedly sold the handgun to Chea Sokhom for $150.

The two security guards told police that Chea Sokhom had invited them to join in a plot to hold the school's students for ransom, police said.

"We have not seen any other motives other than that at this stage," Bou Bunhang said after charging the suspects in court Sunday.

Chea Sokhom earlier told interrogators he initially planned the raid as revenge against a South Korean man who employed him as a driver. He said he had been humiliated when his employer struck him in a fit of anger, so he quit and planned to kill the man's two children, whom he used to drive to the school each day. The two children were unharmed.

Aing Mearadey, an investigating judge, said he has up to six months to investigate the case before the trial starts.

The seven suspects were to be transferred later Sunday from police detention to a prison, where they will remain during the investigation period, he said.