Gen. George Casey, the Army's chief of staff, and Army Secretary John McHugh are set to be keynote speakers at a ceremony at 1 p.m. Friday honoring the dead and wounded, the San Antonio Express-News reported.
The event will take place at Cameron Field, and attendees include Fort Hood commander, Maj. Gen. William Grimsley.
An attorney for the shooting suspect said the ceremony would make it harder for his client to get a fair trial.
"If you were going to ask me whether (Casey's) presence contributes to an environment that makes it more difficult to get a fair trial, I would say yes," said retired Army Col. John Galligan, lead attorney for Maj. Nidal Malik Hasan, who is charged with killing 13 and wounding 32 others on Nov. 5, 2009.
A Fort Hood spokesman said Casey's appearance had no bearing on any legal proceedings.
"It is an important mark in the history of Fort Hood and Central Texas that we should pause and reflect," said Grimsley, the post's senior commander.