A 17-year-old former student has been charged with attempted murder after an alleged knife attack at a northeast Calgary high school forced the school into lockdown Thursday afternoon.Calgary police say officers were called to Lester B. Pearson High School, located in the 3000 block of 52 St. N.E., at approximately 12:05 p.m. on following reports of a youth armed with a knife inside the school.According to investigators, the suspect was smashing property, threatening students and staff and allegedly attempted to stab another student. As multiple emergency calls came in reporting the suspect's movements throughout the school, administrators placed the school under lockdown.Police said officers arrived within minutes, entered the building and located the suspect, who was taken into custody without further incident.One student suffered minor injuries during the assault but did not require hospitalization.The lockdown remained in effect while officers conducted a room-by-room search of the school to ensure there were no additional victims or ongoing threats. The lockdown was lifted after police confirmed the building was secure.Investigators believe the attack was premeditated..The accused, a 17-year-old former student of Lester B. Pearson High School, has been charged with one count of attempted murder, one count of uttering threats and one count of mischief to property under $5,000.Under the Youth Criminal Justice Act, the accused cannot be identified.He is scheduled to appear in court on June 22."Our officers responded within minutes and acted decisively to ensure the safety of every student and staff member. Thanks to their quick actions, the suspect was taken into custody without further harm," said Calgary Police Service Staff Sgt. Mike Sushelnitsky."Incidents like this highlight just how important lockdown drills are. The preparedness of students and staff may well have saved lives."Police said they are working with the Calgary Board of Education to provide support services for students and staff affected by the incident. The Calgary Police Service's Victim Assistance Support Team is also available to victims and witnesses seeking assistance.Anyone with information about the incident is asked to contact Calgary police at 403-266-1234 or Crime Stoppers anonymously.