When the storm struck El Reno, Okla., last Friday, Lisius said he was leading a tour about a mile away, observing from the field with more than a dozen people.
The storm formed rapidly, and turned quickly toward the southeast -- both unusual signs, he says, that showed it was time to take cover.
"We left. It was not a close call because we took quick action to avoid a close call," he says. "It's what we do on a regular basis."
But for a tour group watching from afar, he says, it's easier to change course than it is for researchers who are up close, measuring details about tornadoes.
"Our mission is to teach people about severe weather, and we can get close enough to a tornado to see it and take good pictures of it, but certainly we don't have to get in the path," he says.
From science to 'soul searching'
Nobody knows exactly how storm chasers Tim Samaras, his son Paul Samaras and Carl Young died in a storm that struck the Oklahoma City area on Friday. Friends and family describe them as dedicated scientific researchers known for putting safety first.
The National Oceanic and Atmospheric Administration says it appears to be the first time researchers intercepting a storm's path have been killed.
Lisius and many other longtime storm chasers say they're devastated and shaken by the deaths of colleagues with such extensive experience and training.
"This is the fist time this has happened," said Tyler Constantini, who has been chasing storms since 1998, "and I'm sure we'll learn a lot from it and, hopefully, do a little soul searching, try to figure out what we need to do to try to stay safer out there."
The deaths should give everyone pause, Eilts says, and experts should weigh whether new guidelines are necessary to keep storm chasers safe.
But Eilts says there's no doubt that studying tornadoes on the ground is crucial.
"Our whole country's built upon research and development and enhancement. Ultimately if we can save 100 lives more every year because we have better tornado warnings, that's worth it," he says. "Being in the field is an important part of that research. That has to go on."