(CNN) A Chicago city lawyer has resigned after a federal judge ruled he and another attorney intentionally withheld evidence in a police shooting death case.

A new trail has been ordered in the civil suit.

Darius Pinex was shot and killed during a 2011 traffic stop on the city's South Side

In Monday's ruling, Judge Edmond Chang called for the new trial because city lawyer Jordan Marsh had crucial information that he did not disclose.

"He said the attorney for the city had intentionally hidden evidence, which is very troubling," Steve Greenberg, the attorney for Pinex's family, told CNN affiliate WBBM . "It shows that this culture of indifference to finding out the truth, to holding people accountable, goes up to the highest levels."

The city's Law Department called the conduct unacceptable and said steps have been taken to make sure it won't happen again.

Marsh submitted his resignation on Monday, the city's Law Department said. Another attorney, Thomas Aumann resigned in August.

"The Law Department holds its employees to the absolute highest professional and ethical standards and does not tolerate any action that would call into question the integrity of the lawyers who serve and represent the City of Chicago," the Law Department said in a statement Monday. "The conduct outlined by the court ... is unacceptable."

A jury decided in favor of the police in April, but Chang's ruling means the case will be retried because the information withheld by city attorneys may have cast doubt on some of their claims

"Me and my family wants to move on," Darius Pinex's mother, Gloria Pinex, told affiliate WLS. "That's all me and my family are asking for. Indict the cops and fire anyone who covered-up my son's murder."