Thomas Kim's previous court appearances were canceled because of a medical issue.
He is charged with murder in the shooting death of Long Beach FD Capt. David Rosa, as well as the attempted murder of another firefighter and a resident of the complex.
Rosa, 45, was fatally shot while searching for victims in an explosion at the senior living facility. Kim is accused of triggering the explosion designed to kill his upstairs neighbor and then shooting firefighters who responded to the blaze.
David was a 17-year veteran of the Long Beach Fire Department. He leaves behind his wife and two children.
Kim's arraignment was delayed until Aug. 15 due to medical issues and not being able to communicate with an attorney.
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City News Service contributed to this report.