Motive Unknown As Police Investigate Deadly Grocery Store Shooting

The motive behind Monday's deadly shooting at the King Soopers store in Boulder remains unknown.

Video Transcript

- Well four days after the murder of 10 people at the King Soopers in Boulder, we still don't know what set off the gunman. The memorial outside the store is massive, still growing. You can see all the people outside the fence there in that view from Copter 4.

CBS4's Rick Sallinger live tonight at Boulder Police headquarters. And Rick, we heard from investigators today, but nothing about why this store was targeted.

RICK SALLINGER: Well, Jim, they provided the information here at Boulder Police headquarters. No major breakthroughs were announced, just a lot of painstaking investigative work.

They came with expressions of sorrow and prayer and symbols of patriotism for the fallen officer.

JOE DURAN: His actions are beyond belief because bravery is-- he's a hero.

RICK SALLINGER: In front of the patrol car being decorated with flowers and tears, Boulder's police chief had no breakthrough to announce for the reason behind the massacre.

MARIS HEROLD: It'll be something haunting for all of us until we figure that out. And like someone said, sometimes you just don't figure these things out. But I am hoping that we will.

RICK SALLINGER: What they do know is the AR-556 pistol used by the gunman was legally purchased at the Eagle's Nest Armory in Arvada after passing a background check.

MICHAEL DOUGHERTY: The FBI, CBI, and all the law enforcement agencies involved are doing a deep dive into the offender's background as well as the background of everybody involved in this incident-- victims, witnesses, and so forth.

RICK SALLINGER: Among those hoping for answers is Robin Kirkbride, who came to pay her respects. She was in the grocery store not long before the gunfire broke out.

ROBIN KIRKBRIDE: Oh, it could have been me. My life flashed in front of my eyes. You know, I've got kids and grandkids.

RICK SALLINGER: It is too late to change what happened, but not too late to try to learn why.

We contacted the store that sold the gun that was used in the killings and it issued a statement, which reads, in part, "Ensuring every sale that occurs at our shop is lawful, has always been and will always remain, the highest priority for our business."

Now, the defendant in this case is no longer in the Boulder County Jail. He has been moved to another facility due to threats made against him.

Live in Boulder, Rick Sallinger, covering Colorado First.