Accused Pentagon shooter pleads guilty ALEXANDRIA, Va. - An ex-Marine from Virginia pleaded guilty Thursday and has agreed to serve a 25-year prison sentence on charges that he fired a series of overnight pot shots in 2010 at the Pentagon, the Marine Corps museum in Quantico and other military targets as part of what prosecutors called a campaign to strike fear throughout the region. Prosecutors also revealed Thursday new details about Yonathan Melaku's intended next target: Arlington National Cemetery, where he was arrested before he was able to carry out a plan to deface gravestones there. As part of Thursday's plea deal, Melaku, 24, of Alexandria, pleaded guilty to destruction of U.S. property, use of a firearm in an act of violence and intention to injure a veterans' memorial, namely the cemetery. Prosecutors and Melaku's lawyer agreed to a 25-year sentence as part of the deal, and U.S. District Judge Gerald Bruce Lee said he would agree to the sentence as well. Formal sentencing was delayed until April so a pre-sentence report can be prepared and Melaku's lawyer can request a mental-health evaluation for his client. Prosecutors also released a video, made by Melaku, that was part of the evidence in the case, in which Melaku is seen firing shots at the National Museum of the Marine Corps as he drives by from I-95, where the museum is easily visible. In the video, Melaku shouts "God is Great!" in Arabic and talks about targeting the museum and "turning it off permanently." Pentagon scare suspect linked to D.C. shootings Pentagon scare suspect charged in D.C. shootings The overnight shootings in October and November of 2010 twice targeted the Marine Corps museum and once each targeted the Pentagon and military recruiting stations in Woodbridge and Chantilly. The shootings raised a high level of concerns, prompting authorities to suspect they were related and conducted by an individual with a grievance against the military in general or the Marines specifically. But the shootings went unsolved until this summer, when Melaku -- a naturalized U.S. citizen from Ethiopia -- was spotted by police on Fort Myer and ran off, leaving a backpack behind. He was later caught and arrested at Arlington National Cemetery. The incident prompted a massive security scare in and around the Pentagon. In the backpack police found spent shell casings; five pounds of ammonium nitrate, a common material in homemade explosives; two cans of spray paint; and a notebook in Arabic that contained references to Osama bin Laden, the Taliban and the "path to jihad." Melaku eventually admitted to authorities that he planned to desecrate grave markers in the cemetery by spraying Arabic graffiti on them, and to deliberately leave the ammonium nitrate behind. Nobody was hurt in any of the incidents, but Melaku has been ordered to make $111,000 in restitution for the damage he caused to the buildings, including the Pentagon. Though no one was hurt, FBI spokeswoman Jacqueline Maguire called the case serious, and credited investigators for arresting Melaku before he did worse. She noted that a search of Melaku's home produced evidence that Melaku was looking to build a homemade timer. The defense lawyer, Gregory English, said he has no doubt that his client is legally sane, but said a proper mental-health diagnosis may help his client become a better person while he serves his sentence. English, himself a former Marine, said after the hearing that his personal experience suggests it's possible that some sort of post-traumatic stress or dispute with the Marines may have triggered Melaku's actions rather than any desire to support al Qaeda or the Taliban. "The facts of the case and what his parents are saying to me about the young man suggests these actions are totally out of character," English said. Dana Boente, the top assistant U.S. attorney for the Eastern District of Virginia, which prosecuted the case, said authorities have no evidence that Melaku suffers from any serious mental-health disorders or that his years in the Marine reserves provided a motive for the crime. He said Melaku never served overseas. Boente called the crimes "a campaign of calculated and sustained attacks against military installations and memorials in northern Virginia." Melaku did not speak during the hearing, except to answer a series of questions from the judge with a soft-spoken, "Yes, sir" and a final "guilty, sir" to formally enter his plea.