Four people have been charged with constantly threatening a Queensland school located at Brisbane’s south with bombing signs. All of them are subject to face Richlands Magistrates Court on Monday.

AAP reported that two young men aged 18 and 19 years old have been the latest arrests after a man, 22, and a woman, 17, were arrested earlier. They have been charged over a hoax bomb threat to Calamvale Community College. Almost 20 schools have been targeted to make fake claims of bombs located at the institute’s premises. The four suspects are due to be presented in court for disturbing the state intentionally.

The college received threatening calls from the suspects this week. However, it was yet not clear why the alleged culprits targeted this institution specifically. Police confirmed that threatening calls were made to the school on Wednesday at about 12:40 p.m. which prompted immediate evacuation. After the investigation, it was found that the threat was unsubstantiated.

After the arrest of the earlier two suspects, the police continued the investigation. Superintendent Mark Reid warned people that whoever is found guilty of conducting the offense was likely to face a maximum five years of jail term. He claimed that the police might not have gathered the call details, but they could find some clues to detect the loopholes.

Reid said that the community involved in such criminal activities is exhibiting a behaviour that indicated targeting children. “It targets probably one of our most vulnerable groups, which are our children,” Yahoo News quoted him as saying on Saturday. “It’s very traumatising for the children themselves, and puts a lot of pressure on the families as well trying to get down to the school.”

One of the four charged suspects has already faced court on Monday on a fake bomb plantation at Brisbane’s school. However, the issue was adjourned to March 21. The rest of the three suspects are still waiting to face court later on the same day.