“The officers engaged in reckless tactical decision making, they unreasonably placed themselves in harm’s way, and Officer Loehmann’s use of deadly force was excessive, objectively unreasonable and inconsistent with generally accepted police practices,” wrote Jeffrey J. Noble, a former deputy police chief in Irvine, Calif., in his report.

Mr. Noble’s report, as well as one written by Roger A. Clark, a former lieutenant in the Los Angeles County Sheriff’s Department, reached a conclusion opposite of those previously released by prosecutors. The earlier reports found that Officer Loehmann had reasonably feared for his life and that the split-second decision to shoot Tamir could be justified under the circumstances. Tamir had been carrying a replica gun given to him by a friend.

Lawyers for the Rice family have criticized the Cuyahoga County prosecutor, Timothy J. McGinty, for his handling of the case and have requested that he step aside and appoint a special prosecutor. The family has labeled the shooting as unjustified and called for criminal charges against Officer Loehmann and his partner, Officer Frank Garmback, who was driving the police car but did not fire his gun.

Mr. McGinty has said he was releasing expert reports and other investigative documents as they became available, in the interest of transparency. Months ago, he invited the Rice family to submit its own reports for consideration by grand jurors. Prosecutors have not said when grand jurors will decide whether to indict.

“Our stated policy in all use-of-deadly-force cases is to welcome all relevant evidence and let the grand jury evaluate and make the decision,” Mr. McGinty said Saturday in a statement about the new reports. “This process is a wide-open search for the truth.”