Suspect Luigi Mangione remains jailed in Pennsylvania, fighting extradition.
Investigators have already developed evidence that includes fingerprints and shell casings that allegedly match a gun found in Mangione's possession.
Meanwhile there is additional controversy over public support for Mangione expressed online and through fundraising efforts.
One crowdfunding site raised more than $50,000 for his legal defense fund from more than 1,500 donors, ABC News reports.
Another site, GoFundMe, took down a similar effort on its platform, saying it does not allow legal defense funds for violent crimes.
In the Inland Empire, a billboard has gone up declaring "Free Luigi Mangione / He's a Hero."