The man who opened fire in a classroom at Virginia’s Old Dominion University completed a drug treatment program that allowed him early release from federal prison, even though he was convicted of a terrorism charge that should have disqualified him from that benefit.

U.S. officials have said taking out a terrorist threat in Afghanistan with no American troops on the ground would be difficult but not impossible.

The shooting this week of 10 people by a man who deployed smoke grenades and fired at least 33 shots in a commuter-packed Brooklyn subway car was hardly the first time New Yorkers have grappled with an act of violence.