During a recent visit to a National Guard training facility outside Peekskill, N.Y., Mr. Card, an Army reservist, had a run-in with officials and was later evaluated at a mental health facility, according to a senior law enforcement official. But the Maine commissioner of public safety said on Saturday that he had no information to suggest that Mr. Card had ever been forcibly committed for mental health treatment.

When he tried to complete the purchase of the gun silencer in August, Mr. Card admitted to having mental health issues on a Form 4473, a federal document that must be filled out and signed in order to retrieve the device. Form 4473 is used to determine whether someone can receive a firearm or firearm equipment after having made the purchase.

Officials have said that Mr. Card had legally purchased his weapons, which means he passed background checks that include evaluating whether he was mentally fit to own a firearm. It is unclear whether he had admitted to his mental health issues in previous forms that are typically required at the time of purchasing the weapons.

One of the questions on the form was, “Have you ever been adjudicated as a mental defective OR have you ever been committed to a mental institution?” Mr. Card checked the box, indicating yes, according to Mr. LaChapelle, who is also a city councilor in Lewiston.

The staff at the gun shop waited until Mr. Card signed the document before declining to give him the silencer. Mr. Card, in response, “was very cordial, very polite,” Mr. LaChapelle said.