Police believe his death was the result of an attempt to steal Williams' Jeep Grand Cherokee.
The number of flowers continues to grow at a memorial outside the popcorn shop, and the amount of money being offered for any information that leads to an arrest in the case is growing, too. It's now reached $34,000.
Police search for killers of retired Chicago firefighter
"What we are asking for is for the public to come forward and give us any little tip they may think they have, if this reward can trigger somebody to come out and provide information and get these individuals off the street before they commit harm to another family," Chicago police Deputy Chief Migdalia Bulnes said.
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Adding $10,000 to the pot Sunday, the organization "I'm Telling, Don't Shoot" has announced it has also hired an attorney to file a class action lawsuit against the manufacturers of certain vehicles, Jeeps among them, which in recent months have increasingly become the target of would-be thieves and carjackers armed with programming devices that can remote start a vehicle without the key fob.
Friends, family remember Chicago firefighter; police search for killers
"This issue of being able to hack into vehicles has been an ongoing issue. It's our position that this needs to be addressed by the makers," said Benjamin Kelly, with Vrdolyak Law Group. "This is creating a higher incidence of risk to members of the community and, more importantly, the owners of those vehicles."
RELATED: 2 charged with attempted murder in connection with Chicago carjackings, police say
And while police said there is no evidence to confirm that Williams' killers were attempting to engage in that kind of high-tech theft, they do say it's been an increasing problem over the last year, which might partly explain the dramatic increase in this type of crime.
WATCH: CFD, CPD salute Lt. Williams as body arrives at medical examiner's office
Retired CFD Lt. Dwain Williams honored as body arrives at Medical Examiner's Office
As of Nov. 20, 1,125 vehicles had been carjacked in the city of Chicago. That is compared to 501 at the same time last year.
Anyone with information that might lead to an arrest in Williams' murder can submit a tip anonymously at CPDtip.com.