Iranian Cyber Army or the American Cyber Army?

A recent event that shocks and alarms all twitter users, making all there personal cyber informations vulnerable to exploitation or piracy as a whole. A claim says that they are the Iranian Cyber Army, showing their national flag as a protest against USA. Now my questions is, how true is this? Is really the Iranians who did hacking Twitter or it is USA itself who hacks Twitter and points its finger to Iran as the culprit.

We have known that the relationship between Iran and USA is in big question mark due to nuclear issues and because of this reason I do suggest that a thorough investigation must be done before we will point our fingers to somebody else.