Before the shooting Mr. Wong had been arrested, cited or had some minor contact with the police at least five times since 1990, but details about the cases remain unclear. At the time of the shootings, he was not a subject in any investigation, nor did he have a documented mental health issue.

March 2008 Mr. Wong bought the first gun, the Beretta 92, at a store in Johnson City, N.Y. He passed a background check.

March 2009 Mr. Wong bought the second gun from the same store, but his background check was not approved immediately. He received the gun under a federal rule that allows a gun to be sold if the background check system does not return a decision in three business days.