The grizzly took Jerry Ruth by surprise, bursting from thick brush and biting his jaw almost completely off.
On the ground and barely able to see, Ruth grabbed his .41 Magnum-caliber revolver and started shooting. The third bullet pierced the bear's heart and spinal cord, killing it from 25 feet.
"I'm glad I was armed with a firearm and I'm glad I was able to shoot straight," said Ruth, attacked last July 19 a couple miles from his home not far from Yellowstone National Park.
Ruth's gun quite possibly saved his life. It also provided fodder for a long-standing debate about whether a gun or bear spray is better in fending off a grizzly attack.
And if that sounds like an esoteric discussion, it has intensified with a new federal law allowing people to carry guns in national parks.
The advent of the new law focused not on bears but on Second Amendment rights. Even so, three national parks -- Glacier, Yellowstone and Grand Teton -- are waiting to see what will happen once hikers and campers begin venturing into the backcountry in the weeks ahead.
"Experience shows that putting firearms and grizzly bears in the same place ends up with dead grizzly bears," said Steve Cain, senior biologist for Grand Teton National Park.
"Time will tell. Of course there is the potential for unintended consequences -- injury to bears, injury to people," said Glacier spokeswoman Amy Vanderbilt.
Grizzlies are the undisputed bosses of the backcountry in the three parks. They've killed 10 people in Glacier and five in Yellowstone in the past century. Those parks average one grizzly attack with injuries a year. Grand Teton has had only a handful of attacks, and no deaths, but it's only had substantial numbers of grizzlies for the past decade or so.
Wyoming, Idaho and Montana are home to roughly 1,300 grizzlies. Their numbers have rebounded since the 1970s and, although grizzlies still are listed as a threatened species, it's no longer rare for one lolling roadside to jam up tourist traffic in Grand Teton, Yellowstone or Glacier.
Ruth was attacked not long after he and his wife moved to Clark in remote northwestern Wyoming. He said the 275-pound female grizzly, which had three cubs, attacked while he was hiking with a friend.
"It was like walking down a hallway and somebody jumping out of a doorway," said Ruth, who'd just retired after 28 years as a Baltimore-area police officer.
Ruth counted on his experience and training with guns to ensure that the bear, after its initial attack, wouldn't come back and finish him off, said Mark Bruscino, the Wyoming Game and Fish Department chief bear biologist who investigated the mauling.
"Using a firearm in that situation was completely justifiable," Bruscino said. "He probably could not have lived through another thrashing like the first go-around."
Yet park rangers in Yellowstone, Grand Teton and Glacier are still telling visitors that a pressurized can of hot-pepper oil -- bear spray -- is their best defense.
Their reasoning? Studies show that in most cases, putting a cloud of bear spray in a grizzly's face works better than trying to stop a moving 400-pound animal with a perfectly placed bullet.
"You've got to be a really good shot with a gun," said Yellowstone bear biologist Kerry Gunther. "That's the beauty of bear spray. You don't really have to aim it. All you have to do is pull it and pull the trigger."
Bear spray, of course, also happens to be better for bears.
Park visitors used to have to keep their guns unloaded and well out of reach, such as in the trunk. The new law allows visitors to take loaded guns anywhere they're not prohibited by state or federal law.
Bear biologist Tom Smith said he's "absolutely concerned" about grizzlies dying unnecessarily.
An assistant professor at Brigham Young University, Smith used to work at Alaska's Katmai National Park and Preserve, a place famous for drawing large numbers of grizzlies that feed on spawning salmon.
Smith said tourists at Katmai often would tell him they'd been charged -- but that after reviewing video footage they provided as evidence, he never saw a grizzly charging, just bears walking about and minding their own business.
"The point is, people can't read these animals at all," Smith said.
Smith has evaluated the efficacy of bear spray in reported aggressive and nonagressive encounters in Alaska between 1985 and 2006. He found that bear spray stopped grizzlies in 46 of 50 cases, or 92 percent of the time.
Bear spray stopped charging grizzlies 12 out of 14 times, a success rate of 85 percent. The other two times a grizzly charged, one person was deeply scratched and the other was spared when the grizzly moved off after stopping just a few feet away.
"Simply put, if you're just a hiker, you're far better off with the nonlethal deterrent like bear spray. The numbers just speak for themselves," Smith said.
It's also more practical, Smith said: In thick trees and brush where a grizzly could surprise you, hiking with a lightweight can in your hand with the safety off is much easier than holding an unholstered large-caliber handgun.
Shooting a grizzly in a national park will not go without inquiry, unless it is an obvious case of saving your life or someone else's. For one thing, shooting a gun in a national park is still against the law. For another, killing a grizzly, except to defend yourself or someone else, is a federal crime punishable by up to six months in prison and a $25,000 fine.
On top of that, killing wildlife in a national park is a separate crime altogether.
"It gets fairly complex, but it's safe to say these things will be investigated," said Tim Reed, chief ranger for Yellowstone.
In the vast national forests surrounding the three parks, elk and deer hunters encounter and kill grizzlies frequently. In 2008, hunters killed eight grizzlies in self-defense near Yellowstone.
But hunters move stealthily off-trail, more or less ready to shoot -- something hikers typically don't do.
Ruth had no time to use his gun when he was attacked. He shot the grizzly after it went back into the brush to check on its cubs. Even if he had bear spray, twigs and branches could have blocked the spray and made it less effective, he said.
"My situation was pretty dire at the time and I'm not sure pepper spray would have worked at that point," Ruth said.
The three orphaned cubs were taken to the Memphis Zoo.
Ruth spent 12 days in a hospital and is still recovering. He said he and his wife, Cindy, still enjoy backcountry hiking and camping. He still takes his gun.
"You never think that you're going to use it for anything. You just bring it along because you think it would be a good idea," Ruth said.
His wife, who dislikes handling guns, takes bear spray.