Cleveland ? Despite 26 security cameras, officials couldn’t say Thursday how an armed, suspended 14-year-old student was able to get into his downtown school a day earlier and shoot two students and two teachers before killing himself.

School officials also were investigating how a number of warning signs from the troubled student, including threats made last week, apparently went unheeded.

Police were checking surveillance video Thursday for clues as to how Asa H. Coon, armed with two revolvers, was able to enter the SuccessTech Academy alternative school. Police Chief Michael McGrath said a classmate could have let him in a back door.

Coon was a new student at the school, but the district has a dossier on past problems. He had mental health problems, spent time in two juvenile facilities and was suspended from school last year for attempting to harm a student, according to juvenile court records.

He had been suspended for a Monday fight, but students said officials had done nothing about threats he had made last week to blow up the school and stab students.

“I told my friends in the class that he had a gun and stuff,” Rasheem Smith, 15, said Thursday on CBS’s “Early Show.” “We talked to the principal. She would try to get us all in the office, but it would always be too busy for it to happen.”

Responding on the show, schools CEO Eugene Sanders said the district would investigate. A message left at Principal Johneita Durant’s office was not returned. A phone call to her home was not answered.

The school of about 240 students has metal detectors but none were operating Wednesday. Students said the devices were used only intermittently.

When asked how Coon got past an armed security guard or whether warnings signs were missed, the police chief said he couldn’t comment. McGrath said police consult with school officials on where to locate metal detectors, based in part on crime in schools.

Charles Blackwell, president of SuccessTech’s student-parent organization, said the position of a second security guard had been eliminated because of lack of money.

Maureen Harper, a city spokeswoman, said Sanders will give the mayor a plan by noon Friday to address whether additional security measures are needed at the school and how the school identifies potential problems among students.