Mayor Don McLaughlin, in a statement on Tuesday, said district attorney Christina Mitchell’s chief investigator was among the law enforcement officers who responded when a gunman killed 19 students and two teachers at Robb Elementary School on May 24, 2022.

Law enforcement officers from several agencies waited more than an hour, while some children called for help, before eventually storming the classroom and killing the shooter.

Her investigator Shayne Gilland’s presence “taints her entire inquiry into any possible criminal conduct by law enforcement,” Mclaughlin said in the statement, in which he also called for Mitchell’s resignation.

Mitchell did not immediately respond to a request for comment.

The city had launched its own probe, hiring a private investigator who reported to Mitchell. Mitchell has refused to provide the city with all the information the investigator gathered, McLaughlin said.

Mitchell told the San Antonio Express-News earlier this week that she planned to present her case to a grand jury by the end of the year, and has said releasing information about her investigation would jeopardise the probe.

The city sued Mitchell to obtain the information, McLaughlin said.