Dzhokhar Tsarnaev, the surviving suspect in the Boston Marathon bombing, was formally charged with federal crimes Monday, specifically destruction of property and using a “weapon of mass destruction” to cause death, a capital crime under U.S. law. A murder indictment by Massachusetts will presumably follow.

The federal government should take the lead in preparing a case against the suspect. Among the questions that demand answers: Where did the bomb-making arsenal come from, and how was the necessary know-how gained to build and set off improvised bombs, including those made of ordinary pressure cookers filled with black powder and shrapnel?

Did others give advice or instruction? Where did the funds come from to make the deadly purchases?

These questions reach across state lines. Boston’s police commissioner said he believed more death and mayhem were planned. Three people were killed in the bombings, and a fourth in a shootout early Friday.

The suspects reportedly planned to head to New York the night they were tracked down. Were they acting alone or did they have a support network? Are there other threats connected with this case?

These questions could be better put to a suspect who is properly determined to be an enemy combatant. Unfortunately, the administration denied that option Monday because Dzhokhar Tsarnaev is an American citizen. He was sworn in as a naturalized citizen last September.

Sen. Lindsey Graham, R-S.C., noted on Monday that all evidence points to the likelihood that the Boston bombings were inspired by radical ideology, as were the attacks on 9/11.

Sen. Graham pleaded for the administration to keep the military combatant option on the table.

A military judge advocate of long standing, Sen. Graham noted that the suspects weren’t involved in robbing a bank or some similar crime. Rather, he said, the evidence is “ample and overwhelming that the suspects in Boston were inspired by radical jihadists and their ideology.”

An alternative option would be to invoke the public danger exception to the Miranda rule, also allowing the suspect to be questioned by the nation’s top interrogators, the High Value Detainee Interrogation Group created by President Obama in 2009 to replace CIA interrogators. The public danger exception allows law enforcement authorities to delay notifying a suspect of his rights to remain silent and have counsel.

The risk in this case is that a court might reject evidence obtained before the suspect was read his rights. It would be a risk worth taking if investigators have reason to believe they will be able to uncover a broader terrorist conspiracy.

But the risk could be avoided if Dzhokhar Tsarnaev were dealt with as an enemy combatant.

Also needed is a clear answer to the charges made by Rep. Michael McCaul, R-Texas, chairman of the House Homeland Security Committee, and Rep. Peter King, R-N.Y. the former chairman. In a letter to Attorney General Eric Holder and the FBI, they say that the Boston bombing represents an “intelligence failure,” in part because of the FBI’s failure to find any suspicious behavior by Tamerlan Tsarnaev, the older brother who died during a shootout with police early Friday morning.

In 2011 Russia requested FBI help in identifying Tamerlan Tsarnaev’s radical links, but the FBI found nothing against him. He reportedly visited Dagestan and Chechnya last year, areas of Russia where radical Muslims operate, but that does not seem to have drawn attention to his activities.

There is plenty to investigate in this case. At this point the priority should center around the possible existence of a supporting network exists that continues to pose a wider danger to American citizens.