The enemy within.

(Fox News) — Officials say they have evidence linking a Marine reservist who was detained near the Pentagon last week to the 2010 shootings at several D.C.-area military buildings.

The officials said Wednesday authorities are investigating Yonathan Melaku in the shootings.

Melaku was detained Friday after he was spotted carrying a suspicious backpack near the Pentagon containing what initially was feared to be bomb-making material. Authorities said the items were not explosive.