The male black-and-white cat was found in the lagoon on Nov. 2 with a 5-pound dumbbell tied around its neck. It was discovered by Redwood City public works employees, who brought it to the humane society, shelter spokesman Scott Delucchi said.
The dumbbell was attached to the cat's neck with zip ties, Delucchi said.
The cat appeared to be middle-aged and his front paws were declawed, indicating that he was likely someone's pet and not a feral cat, Delucchi said.
"We continue to believe this was an owned cat and that someone intentionally killed him in an horrific way," Delucchi said.
The nature of the crime indicates clear intent to harm the animal, which is a felony, he said.
The humane society announced it was offering a $1,000 reward for information leading to the arrest and conviction of those responsible for the crime on Nov. 3, but that reward has grown quickly after donations from individuals and businesses.
A humane society veterinarian conducted a necropsy last Friday that revealed the cat was alive when it was dumped in the lagoon with the weight around its neck, according to the humane society. It was in good health for a senior and had no obvious injuries or illnesses.
No one has come forward as the cat's owner. The cat did not have a collar or an identification microchip.
"We've not found any lost cat reports from our county or surrounding counties matching this cat, which indicates the owner may know who is responsible but is afraid to come forward for fear of retaliation," Delucchi said.
Anyone with information about the crime is urged to call the Peninsula Humane Society at (650) 340-8200 or email at firstname.lastname@example.org.