1.   Police officers did not disclose a motive for the shooting.

2.   Police have identified no suspects in the killings, nor have they disclosed a motive.

3.   The authorities have not disclosed a motive for the killings.

4.   Police did not disclose any motive for the bombings.

5.   Police have not disclosed a motive for the killing.

6.   Police have not disclosed a motive or said whether they are looking for other suspects.

7.   Authorities have not disclosed a motive in the four slayings.

8.   Inoue confessed to the attack but refused to disclose a motive, a police official said, speaking on condition of anonymity.

9.   Investigators did not disclose a motive but ruled out murder-suicide.

10.   Police spokesman Joji Fujiha said the suspect admitted to the hijacking but would not disclose a motive.