Holmes had reportedly amassed more than 6,000 rounds of small arms ammunition from online arms merchants and had the bullets delivered by private carriers that may have included FedEx and United Parcel Service.

Memphis-based FedEx and Atlanta-based UPS said Monday they were cooperating with investigators and took a relatively low profile about possible involvement in the alleged shooter’s supply chain.

While the U.S. Postal Service does not carry live ammunition, FedEx and UPS routinely do so under special conditions imposed on hazardous cargo.

Asked about reports of a surveillance video showing Holmes picking up 150 pounds of ammunition at a FedEx outlet in Colorado, FedEx issued this statement:

“Our thoughts and prayers are with those impacted by this terrible tragedy in Colorado. We have a long-standing history of close cooperation with law enforcement agencies. Any questions regarding the investigation should be directed to authorities.”

A spokeswoman said UPS was cooperating with investigators and hadn’t confirmed whether the suspect received ammunition deliveries by UPS.

“While we are cooperating with the FBI for further investigation, it was erroneously reported (Sunday) that our drivers had been interviewed by authorities,” said sporkeswoman Susan Rosenberg. “This didn’t happen for any drivers that delivered to either the suspect’s residential or university addresses. If a reporter talked to any UPS driver, then all they heard was anecdotal about our delivery process in general but they wouldn’t have any information to the specific addresses. We’re still reviewing data, so we have no specific confirmation on deliveries or corresponding shippers.”

CBS News reported on “Face the Nation” Sunday that authorities had learned the suspect shopped online outlets such as BulkAmmo.com and TacticalGear.com and that a UPS driver told authorities that 90 packages had been delivered to Holmes’ work address.