Rita Ruiz de Guillen remembered her son Alonso as a caring person with a big heart.
"My son went to a place where there are no borders. God never places borders," she said.
And, she said, the images of people stranded in Houston floodwaters affected Alonso deeply. That's why last Tuesday, he and a friend drove 120 miles from Lufkin, Texas, to Houston to rescue people stuck in an apartment.
They were in a boat that hit a bridge and capsized. He and his friend went underwater.
Guillen came to the U.S. from Mexico when he was 15 to live with his dad, a permanent resident. He signed up for DACA, and as a "Dreamer," was working toward citizenship.
Guillen's mother supports DACA, and says there are other young Dreamers who share her son's spirit and who are making this country great.
"The U.S. should see that there is a lot of future for these young people. If they get the opportunity, they'll do a lot for this nation. That's what they should be thinking about. People like Alonso," she said.
Residents in his adopted hometown are raising money for his funeral.
© 2018 CBS Interactive Inc. All Rights Reserved.