Storm-chasers monitor weather activity and seek to raise the alarm, hoping to save lives in threatened areas.
Oklahoma's Storm Prediction Center told AP the three went all over the Great Plains studying the massive storm and raising awareness about the kind of danger it posed.
Meteorologist Tim Samaras, 55 years old, his 45-year-old partner Carl Young, and 24-year-old son Paul Samaras, died near El Reno on Friday, according to family members.
ABC News put the death toll at 11 after 165-mile-an-hour winds pummeled the Oklahoma City area Friday evening.
Samaras, an engineer, had been fascinated with tornadoes for the past 30 years. He had become such an expert that he was a regular on Discovery Channel "Storm Chasers" show, said AP.
"I'm not sure exactly why I chase storms," Samaras explained in a Youtube video cited by ABC. "Perhaps it's to witness the incredible beauty of what Mother Nature can create."
Canadian County Undersheriff Chris West told AP the three "put themselves in harm's way so that they can educate the public about the destructive power of these storms."
Jim Samaras posted a statement on his brother's Facebook page early Sunday, saying:
"It truly is sad that we lost my great brother Tim and his great son, Paul. Our hearts also go out to the Carl Young family as well as they are feeling the same feelings we are today," it said, according to ABC.
"They all unfortunately passed away but doing what they LOVED. Chasing Tornado's. I look at it that he is in the 'big tornado in the sky...'" the statement said.
Discovery Channel told AP it is producing a show on the three storm-trackers, which is set to air Sunday night.