Video showed the owner and two other women struggling several minutes in vain to pull the dog off the sea lion. As his daughter screamed and cried, Kelly arrived and grabbed the collar. He shook the dog's head until it released the bloodied mammal, which later died.
Kelly is married to former U.S. Rep. Gabrielle Giffords, who was wounded in a shooting in Tucson, Ariz., in 2011. His daughters, Claudia and Claire, are from a previous marriage.
Laguna Beach police said they did not plan to press charges because it did not appear the owner was at fault in the attack Saturday, Capt. Jason Kravetz said Tuesday. The bulldog mix was leashed and legally on the beach below the exclusive Montage Resort.
Kravetz said, however, that authorities could not close the case until a necropsy is performed and investigators have checked with animal control in the dog's hometown to see if it has a history of attacks. If there is a history of aggression, authorities could become involved.
The National Oceanic and Atmospheric Administration also does not expect to take legal action, spokesman Jim Milbury said.
"We will have to wait for all the facts to come in, but it appears to be an unfortunate accident," he said.
Federal law protects marine animals. The state has no jurisdiction, a spokeswoman said.
The Pacific Marine Mammal Center will determine the sea lion's cause of death. Officers had removed the same sea lion from a storm drain earlier in the day, Kravetz said. Calls to the mammal center were not immediately returned.
"This is a regrettable and traumatic incident for the animals and the people involved," said Madeline Bernstein, president of the Society for the Prevention of Cruelty to Animals Los Angeles. "Perhaps this will lead to more research and recommendations for peaceful coexistence between domestic animals and local wildlife."
Chasing, hunting or attacking animals like cats and squirrels comes naturally to some dogs, PETA said in a statement. In this case it was a vulnerable sea lion.
If the dog has not shown any other signs of aggression, the family should take new precautions and do all they can to make sure no future incidents occur. "But they should not punish the dog," the statement said.
Giffords was not present during the attack, according to a spokeswoman for the gun control advocacy group the couple recently started.
"Mark was alerted to the situation and came to the beach himself," said Jen Bluestein of Americans for Responsible Solutions.
Gun advocates seized on the incident to criticize Kelly, who has called for background checks for gun buyers.
Several people suggested on his Facebook page Tuesday that background checks might also be considered for dogs whose owners can't control them or those that are a threat to the public.