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Jim Cole, Associated Press
Police talk with Manchester West High School students after a 90-minute lockdown was released Thursday Sept. 25, 2014. Police arrested Damian Johnson, 21, a former student after he showed up in a classroom with a pellet gun in his waistband.

MANCHESTER, N.H. — A 21-year-old man who caused a lockdown at his former high school when a student spotted a gun tucked into his waistband had gone there to ask a teacher for a letter of recommendation to college, police said Friday.

Before entering the teacher's classroom at Manchester High School West on Thursday morning, Damian Johnson had put the gun and a knife into a female student's backpack, a police affidavit said.

Until then, the gun was in his waistband and was seen by another student, who reported it to a school resource officer, police said. That led to the 90-minute lockdown.

The student with the backpack gave police permission to search it. The gun turned out to be a pellet gun.

Police said the teacher recognized Johnson as a former student. He did not have a visitor's pass.

Johnson was arraigned Friday on a felony count of falsifying physical evidence and misdemeanor counts of criminal trespass, violation of probation and disrupting school in session. He was jailed on $20,000 bail.

Manchester Police Chief David Mara said at no time did Johnson make a threat or act violently when he was taken into custody.

Johnson's lawyer, William Schultz, declined to comment after his client's brief appearance in court. Johnson mouthed, "I love you" to a woman who was part of a group of family and friends in the courtroom. The group declined to comment afterward.