Officials said a man was swimming when he became caught in a rip current. The man's son-in-law attempted to assist him, but was also caught in the current.
According to deputies, a third person swimming nearby heard cries for help and ran in to assist.
Deputies said the good Samaritan was able to bring the man ashore, but he was already dead.
The son-in-law was pulled from the water by his son. That second victim was initially conscious upon coming ashore, but later passed out. Authorities say he was taken by air ambulance to a hospital where he died.
The bystander who tried to help took in water, but authorities say he is expected to be OK. The son, who was the fourth person in the water, was not injured.
The victims and their family members were vacationing in the Treasure Island neighborhood.
Authorities warn that the San Luis Pass area has been experiencing heavy rip currents.
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