CNN  — 

A gunman who killed a woman and wounded at least 14 other people at a western Tennessee Kroger before apparently killing himself this week was a third-party vendor for the store, police said Friday.

UK Thang, 29, was the man who shot 10 employees and five customers Thursday afternoon at the Kroger in Collierville, some 30 miles southeast of downtown Memphis, police said.

Investigators are still trying to determine a motive, Collierville Police Chief Dale Lane said at a news conference Friday morning.

“We all want to know the ‘why.’ But today, less than 24 hours (in), we’re not ready to tell you that,” Lane said.

The gunman opened fire around 1:30 p.m., sending numerous people running for cover in freezers, offices and elsewhere, police said.

The woman who died was Olivia King, Lane said Friday. She was a customer, according to Kroger.

“Our family is devastated by this senseless act of violence,” King’s family said in an earlier written statement to CNN affiliate WHBQ. The asked for prayers “for all families and friends affected by the events today, as well as for God’s mercy on the shooter and his family.”

Three shooting victims were in critical condition Friday at Regional One Health Medical Center in Memphis, said Dr. Andrew Kerwin, the hospital’s trauma and critical care director.

Some of the injured have been released from hospitals, Lane said. The names of the survivors were not immediately released.

The shooting was over minutes after police received a 911 call, and investigators believe the gunman fatally shot himself “as we were pulling up to the scene,” Lane said.

Police and Kroger officials have not said what service the gunman had performed as a third-party vendor.

The incident was one of at least 517 mass shootings in the United States so far this year, according to the Gun Violence Archive. CNN and the GVA identify a mass shooting as a shooting that injured or killed four or more people, not including the shooter.

Wes King, Olivia’s son, said his mom was shot in the chest. “This type of crime needs to stop being glossed over and sanitized. No one deserves this,” he wrote on his Facebook page.

Police said earlier the gunman had killed one person and shot and wounded 13 others, and a separate person checked into a hospital with an anxiety attack.

Olivia King, right, with son Mark King.

People hid in freezers

Witnesses and police described scenes of chaos and desperation at the store.

Jason Lusk told CNN he was leaving a tool store beside Kroger when he saw people running out of the store screaming there was a shooter.

When he didn’t see anybody initially, Lusk said he began walking toward his car. “That’s when I heard about 10 to 15 shots fired. Sounded like they were directly over my head. Very close proximity. Sounded to me to be a high-powered semi-automatic rifle,” he said.

Another witness, Brignetta Dickerson, was working a cash register when the shooting began in the deli section, she told reporters Thursday.

She and some coworkers and customers ran to the back of the store and through the receiving department. But the shooter eventually moved behind them and began firing, she told reporters with CNN affiliates WMC and WHBQ.

“He kept on shooting, shooting, shooting,” Dickerson said. “He shot one of my coworkers in the head, and then shot one of the customers in the stomach, and then my other customer got kind of like cuts because of the asphalt.”

Dickerson, who said she has been working at Kroger for nearly 32 years, was scared and shaky after the shooting, but overall was feeling OK.

When police arrived, “we were pulling people out of freezers; we were pulling people out of closets,” Lane told CNN on Friday.

Some people “were (down on the ground) pretending to be shot,” and an employee who ran to the roof was eventually escorted down, he said.

“They were doing what they had been trained to do: Run, hide, fight,” Lane said Thursday.

Kroger said Friday it was “horrified and heartbroken over the senseless violence that occurred.”

“In the hours since the shooting, we’re learning of truly heroic acts that included associates, customers and first responders selflessly helping to protect and save others,” Kroger said in a prepared statement. “We will remain forever grateful to the first responders who so bravely responded to protect our associates and customers.

“The entire Kroger family offers our thoughts, prayers and support to those impacted by this tragedy, including our associates, customers.”

The United Food and Commercial Workers International Union, which represents the workers at the Kroger supermarket, said it’s working with the local chapter to help those affected by the shooting.

“We are heartbroken that another act of senseless violence has occurred at a grocery store,” union president Marc Perrone, said in a written statement. “There are no words that can express the impact these horrific acts of violence have on workers, our union members, and our customers.”

Shootings have happened in at least two other grocery stores this year. In March, a mass shooting in Boulder, Colorado, left 10 people dead. And one person was killed in a supermarket shooting in West Hempstead, New York, in April.

CNN’s Melissa Alonso, Andy Rose, Ryan Young, Devon M. Sayers, Matthew Stucker, Rebekah Riess, Jenn Selva and Steve Almasy contributed to this report.