The Latest: Chicago officer tells of shooting black teenager

CHICAGO (AP) — The Latest on the trial of a white Chicago police officer charged with murder in the shooting of black teenager Laquan McDonald. (all times local):

2 p.m.

A white Chicago police officer charged with murder in the shooting of black teenager Laquan McDonald is telling the jury that he opened fire when McDonald kept "advancing" at him waiving a knife.

Officer Jason Van Dyke testiifed Tuesday that he kept firing because he was not certain that he had struck the teen until the teen fell to the ground.

Van Dyke at times became emotional and wiped tears from his cheeks during his testimony.

In a clear but sometimes halting voice, he said McDonald never let go of the knife even after the 17-year-old fell to the ground.