Jeremy Best was visiting the park when he heard some loud bangs.
"I heard a few bangs over my right shoulder, which I assumed was avalanche control," he said.
Best had no idea it was gunfire until rangers told park visitors to get inside the Paradise Inn.
"They had just said, 'Somebody had been shot,'" said Best.
Two hours later, the SWAT team arrived and ordered everyone to get on the ground with their hands behind their heads. Suspected gunman Benjamin Barnes had fled into the woods in the direction of Paradise.
"They printed off pictures of who they thought the suspect was, and checked faces, one by one, to make sure he wasn't in the building," said Best.
After being safely escorted off the mountain, Best learned of the fate of the friendly ranger he had just spoken to in the lot of Paradise.
"It wasn't until Monday afternoon when I'd awakened and I got online, and saw her face. And I was in shock, having spoken to her just moments before (her death)," he said.
Rangers said Anderson rushed from the parking lot to intercept Barnes' car before he could reach Paradise.
"We could have all been dead," said Best. "I believe she saved our lives."
All 137 people who were inside the inn made it out safely, as did a small group of hikers who had camped out in the snow. In a hikers' forum online, the group members said they were guarded by a helicopter, which dropped a disposable coffee cup bearing a message about the danger in the area.
"Ranger has been shot. Shooter at large. We will keep an eye on you," the message read, according to photos posted on nwhikers.net.
According to the King County Sheriff's Office, Barnes shot at several people at a party in Seattle where guns were willingly displayed. The gunfire erupted after one person allegedly didn't want to give a gun back to its owner. Several hours later, Barnes is believed responsible for the shooting death of Anderson at Mount Rainier.
Barnes was later found dead. An autopsy concluded his cause of death was drowning with the second cause of hypothermia.
The park will remain closed through Friday as rangers seek grief counseling in the wake of their colleague's death.
'It just makes you feel sick inside'
In Eatonville, where Anderson lived with her husband and two young daughters, the grief has spread throughout the community.
At Town Hall, a simple memorial to Anderson sits on the front steps.
"We hear about a lot of tragedy in our line of work here, but this is one of the worst things I've ever heard. It just makes you feel sick inside," said neighbor Gail Elliott.
Elliott, director of the community center in Eatonville, is just one of many goodwill soldiers, waiting to mobilize when she gets word from the Andersons.
"Yes, we have a very generous community," she said.
As police officers help provide the family with the much-needed privacy to mourn and to heal, members of a nearby Baptist church have been helping care for the family.
"We got a phone call, asking for someone from our church to be in charge of getting meals around and helping the Anderson family," said Sandi Wikander.
A crew delivered dinner on Monday, Wikander said, and neighbors are on call to help at a moment's notice.
"The rangers were having a meeting this morning with the Anderson family about what they needed food-wise and otherwise, and then she was going to get back with me and we could coordinate," she said.
Anderson was 34 years old. She is survived by her husband and their two daughters, ages 3 and 1.