Officials in Columbus, Ohio, appealed for calm, patience and investigative help Thursday, hours after a white police officer fatally shot a 13-year-old African-American boy who had apparently brandished a firearm that was later determined to be a BB gun.

Speaking at a news conference, the mayor, the police chief and other officials offered few details about what led to the death Wednesday night of the teenager, Tyre King. They cautioned that the investigation, which will be presented to a grand jury, will not be quick. So far, they said, they do not know of any video recording of the shooting.

“Any loss of life is tragic, but the loss of a young person is particularly difficult,” Mayor Andrew J. Ginther said. “Investigations take time, and I ask for everyone’s patience during this difficult time.”

According to the police, officers responded to a report of an armed robbery in the Olde Towne East neighborhood in central Columbus, and saw three males who matched the suspects’ descriptions. Two fled and officers chased them into an alley, where Tyre pulled what appeared to be a gun from his waistband, the police said, and an officer shot him multiple times.

The officer was identified as Bryan Mason, a nine-year veteran, who fatally shot a man in 2012. His superiors cleared him of any wrongdoing in that episode. He has been placed on administrative leave.

Tyre’s death is one in a long string of deaths of black people at the hands of the police in recent years that have drawn national attention, particularly when video is made public. They have prompted sharp debates about race and policing, intense criticism of the police and, in some cases, civil unrest. One of the most scrutinized cases, and one of the most similar to the one in Columbus, also took place in Ohio: the 2014 death of Tamir Rice, 12, who was playing with a pellet gun in a park in Cleveland.

Columbus officials made it clear that they were acutely aware of that history, saying it was too early to make parallels to Tamir’s case, and insisting that they were striving for openness and community outreach that critics have said were lacking in other cities. They also repeatedly stressed Tyre’s conduct, the credible threats officers face and the gun culture.

“Why is it that a 13-year-old would have nearly an exact replica of a police firearm on him in our neighborhoods?” Mr. Ginther asked. “An eighth grader involved in very, very dangerous conduct in one of our neighborhoods.”