BOULDER — Kip Dixon heard a loud noise and perked up.

Sitting at his desk near the floral department in King Soopers supermarket, Dixon, 66, thought maybe a metal shelf had collapsed. After 14 years of working in the store as a nutritionist, Dixon knew the cavernous space could echo and amplify sounds.

Then he heard the screaming.

"All of a sudden people were running by my desk and they were going 'run, run, shooter, shooter.' And then 'bam,' I hear another loud noise," Dixon said Tuesday.

Police say Ahmad Al Aliwi Alissa, 21, walked into the store Monday afternoon and began shooting randomly. Witnesses said he shot at least one person point-blank outside, leaving bodies sprawled in the parking lot amid shattered glass. Alissa faces first-degree murder charges in connection with 10 deaths, including Boulder police Officer Eric Talley, 51, who was shot as he responded to the frantic 911 calls.