Former Broward County Deputy Scot Peterson is subpoenaed to appear Thursday before the Marjory Stoneman Douglas High School Public Safety Commission.
Members are expected to ask why he didn't enter the building where 17 people were killed Feb. 14 and try to stop the shooter.
Panel members said Wednesday that he was "not a real cop" and "a coward."
Peterson told investigators he didn't know where the shots were coming from and that he heard only two or three.
Broward Sheriff Scott Israel and school Superintendent Robert Runcie are scheduled to testify after Peterson.