OSAKA -- Mamoru Takuma, suspected of killing eight children in a June 8 stabbing spree at an Osaka school, will likely be indicted next month now that doctors have concluded he was mentally fit at the time of the attack, sources said Thursday.

Three psychiatrists concluded that Takuma, 37, was able to tell right from wrong and was perfectly mentally fit when he allegedly stormed the state-run Ikeda Elementary School in Osaka Prefecture, fatally stabbing the eight and injuring 13 other pupils and two teachers, the sources said.

The doctors have already notified prosecutors of their conclusion and are now compiling a report, the sources said.

Law enforcement authorities are planning to indict Takuma on charges of murder and attempted murder upon receiving the report, possibly next month.

Takuma has been detained at the Osaka Detention House since July 8 and has been undergoing psychological evaluation involving weekly interviews and tests.

The doctors were expected to compile their findings and make a final decision by Oct. 7, the end of the detention period.

The suspect, who reportedly appeared to be mentally unstable immediately after his arrest, later admitted to feigning mental illness to escape charges.

The prosecutors, however, decided to conduct psychological assessments on Takuma in consideration of his history of psychiatric treatment.

After a month of testing that concluded early this month, the psychiatrists concluded that he was mentally fit. Psychiatrists will continue their examinations while compiling the report, the sources said.

The Code of Criminal Procedure stipulates that the detention period can be shortened with a court decision.

In a letter mailed to his lawyer, Shigeki Todani, in late July, Takuma apologized for killing the children and said that, if indicted, he will testify at the first hearing of his trial that he wants to atone for what he did by receiving the death penalty.

Bereaved families of the slain children, who began collecting signatures for a petition demanding Takuma's indictment earlier this month, welcomed the possibility.

"I am relieved to hear that the case will not end in a way that allows him to get away with it. I will closely monitor court proceedings," a family member said.

The father of one of the eight victims said the indictment is "a matter of course."

"If he wasn't tried, I'd have thought the current system was flawed," he said. "I want to look squarely at the suspect in court. My eyes will be fixed on him with anger."