Following up this article..Metropolitan Police Department went cautious about guerilla for Tepco
The suspect killed himself in July.
After his death, Tokyo Metropolitan Police Department Public Security Bureau sent the papers pertaining to the suspect (58) case to the Public Prosecutors Office on 8/17/2012.
Public Security Bureau identified him from security camera, investigated his house in June. They found documents to criticize Tepco and nuclear power from his PC.
He was suspected to have thrown molotov cocktail at Central research institute of electric power industry sponsored by Tepco on 4/24/2012, and also at Tepco sales office in Chofu on 6/2/2012.