FERGUSON, Mo. — The chief of police here said Tuesday that he had reconsidered his decision to release the name of the police officer involved in the fatal shooting of an unarmed African-American teenager and would not do so because of concerns about the officer’s safety.

The Ferguson Police Department had said it would release the officer’s name by noon on Tuesday, but then it reversed itself after it said that threats had been made on social media against the officer and the city’s police.

“The value of releasing the name is far outweighed by the risk of harm to the officer and his family,” the police chief, Thomas Jackson, said in announcing a decision that was quickly criticized. The officer has been placed on administrative leave.