CHICAGO (CBS) — The family of the Uber driver who was stabbed to death a month ago has filed suit against Walmart for failing to prevent the shoplifting of the murder weapons.

Police in Lincolnwood say the 16-year-old girl charged with murdering the driver, Grant Nelson, shoplifted a knife and a machete from a Walmart. Police say she walked the aisles with both items in her hands, then walked out the door before she got in Nelson’s car and killed him.

Now, Nelson’s family has filed a wrongful death lawsuit against Walmart and its security personnel for not stopping the shoplifting.

“They didn’t inquire or stop her just to ask does she have a receipt?” the Nelson family’s attorney, Robert Bingle said. “That’s the most fundamental and important failure that we see that caused the death of Grant Nelson.”

Walmart declined to comment on the lawsuit, but said “We believe our associates acted properly, including alerting third party security to a possible shoplifting incident.”