New details on Twin Falls In-N-Out shooting after 3 killed, 7 wounded

Three people were killed and seven others were wounded after a gunman opened fire at an In-N-Out restaurant in Twin Falls, Idaho, on Saturday before turning the gun on himself, local authorities said.

Twin Falls Police Chief Matthew Hicks said Sunday the shooter died from a self-inflicted gunshot wound, identifying him as 24-year-old Chad Williams. Hicks said police are working to determine Williams' motivations that led to the shooting and that his family is cooperating with law enforcement.

Investigators said they are confident the suspect acted alone.

A relative confirmed to CBS News that Christopher Claunch, 59, was killed in the shooting. The president of In-N-Out said one of their employees was among the dead. A representative of the employee's family identified her to CBS News as Ashley Garibay, 23.

The situation unfolded before 2:30 p.m. local time. Social media video obtained by CBS News shows people fleeing a shopping center parking lot as multiple gunshots are heard. In the video, a person carrying what appeared to be a firearm could be seen outside the restaurant opening the doors to a parked sedan.

"First responders faced what was described as one of the most chaotic instances a law enforcement officer can face in their career," Hicks told reporters on Sunday.

The police chief said an off-duty police officer and a civilian engaged Williams and returned gunfire.

"We believe their actions drove the suspect from the scene, preventing further casualties," Hicks said.

Jordan Salinas, a 35-year-old from Kimberly, Idaho, was the private citizen who returned fire at the gunman, the Idaho Statesman reported.

"He did not like it when bullets started firing both ways," Salinas told the paper Sunday morning. He posted a message on Facebook thanking the public for their support and promising to share more of his story when he is able.

Marcus James told CBS News his son, Austin, also ran toward danger to try to confront the gunman, but "intentionally did not draw his firearm" because he didn't want law enforcement to mistake him for the attacker. He said Austin was shot and critically wounded when he "came face-to-face" with the shooter.

Marcus said Austin's wife and a friend, both emergency room nurses, treated Austin at the scene before he was rushed to a hospital.

Braxton Stuebe, who was working at a Dick's Sporting Goods store near the scene, told CBS affiliate KMVT that he too came face-to-face with the gunman.

"A storm of people come in, like five, 10 people come in and specifically this lady, she was yelling, 'There's an active shooter