The FBI's definition of terrorism: The unlawful use of force or violence against persons or property to intimidate or coerce a Government, the civilian population, or any segment thereof, in furtherance of political or social objectives.

He was angry and violent, but he didn't have any objective he was trying to achieve through the act. The objective in terrorism isn't the violence, it's a means to an intended end (such as changes in policy, release of prisoners, etc.).