A reward is now being offered as officials try and track down the shooter.
"I've seen this too much," said Peter Wallerstein from Marine Animal Rescue. "I've seen the brutalization of these animals every year."
Wallerstein has been rescuing marine mammals for nearly three decades. Last week he got the call from a lifeguard. A male sea lion had been shot to death and washed up on Venice Beach.
"She came up dead," said Wallerstein. "She came up right here with a pool of blood around her. All it was doing out there was trying to eat, it wasn't bothering anybody. It was living in its environment."
The sea lion ended up at the Marine Mammel Care Center at Fort MacArthur where all the sick or injured sea mammals are brought if they're found in Los Angeles County.
Of those, 10 percent are injured by humans.
"About three percent of our animals are shot," said veterinarian Lauren Palmer. She takes care of the animals and determines the cause of death. "I think that's an underestimate because we don't do complete analysis of every animal that comes in and dies."
"That's wrong," said sea lion enthusiast Sharon Jacobucci. "Sea lions are precious God's creatures. They're part of our animal community, they're beautiful. We go to Sea World to see these sea lions and they're out there shooting them. I hope they catch them."
The investigation for the shooter and a motive continues. It could result in up to a year in prison and a $100,000 fine.
"It's a painful, slow way to die," said Palmer. "This animal that came in most recently suffocated and or bled to death. There were punctures both in its lung and its abdomen. That's a tough way to go."
"I think that's horrible," said Jacobucci. "Are they crazy? These people are losing their minds. That's ludicrous to hurt a sea lion. I'm appalled by the whole thing."
A $5,000 reward is being offered to anyone who can provide information. Tips will remain anonymous.
Call the Marine Animal Rescue at 800-39-WHALE.