Ultimately, Mayor Sylvester Turner.
Turner immediately told CNN, “We’re not going to leave any stone unturned.” Instead of looking under stones Turner needs to look in the mirror. Houston has a clear hierarchy regarding who’s tasked with public safety at large events and at the top of that food chain is the mayor. This is evidenced right here at this link: MAYOR’S OFFICE OF SPECIAL EVENTS

In Houston, like most major metropolitan centers in America the Fire Chief is an appointed position. Under the Mayor’s supervision the Fire Chief works in conjunction with the Chief of Police to ensure public safety. Fire Chief Samuel Peña also failed the city of Houston with his mishandling and neglect of safety of the Astroworld Festival attendees. Houstonians should not allow Mayor Turner to divert responsibility by scapegoating the Fire Chief. Both should lose their jobs.

Once the fans knocked over the metal detectors and rushed the concert grounds, uncounted and unmonitored, the Fire Chief should have canceled and rescheduled the show. Would the Astros have played as scheduled if this had happened at the World Series? Were the same protective measures to protect the fans from terrorism, mass shootings, and every other eventuality afforded to the festival attendees? Obviously, not. So then ask yourself why some lives are treated as if they’re less than others?
Hindsight may be 20/20 but there was no need have to rely on hindsight in this circumstance. Protocols were ignored and public safety was neglected.
Finally, where was Chief of Police Troy Finner ?

“Leads from the front line during major events…”
Chief Finner, you failed. A crowd with the same capacity as the World Series attended a festival, crashed the gates in the presence of officers who answer directly to you and no action was taken to preserve public safety and eight lives were lost.
Turner, Peña, and Finner need to go. They have failed the city of Houston.
Finally, these are lyrics from Travis Scott’s song Stargazing:
“And it ain’t a mosh pit if ain’t no injuries
I got ’em stage divin’ out the nosebleeds”
This is NOT the person who should be tasked with public safety. He gets about as close as possible to yelling fire in a crowded theater and inciting a riot is a crime. As concert goers and consumers of pop culture it’s up to us where we draw the line. But when it comes to public safety there are people who have accepted the responsibility and those who have not. Mayor and Fire and Police Chief are prestigious and powerful positions. When they fail to do their jobs they must be replaced.