Authorities say a janitor in a commercial building in the 1200 block of Second Street called police after seeing the mountain lion just before 6 a.m.
The area was shut down as Fish and Game officials cornered the cat in a courtyard and tranquilized it. Officials said they tried to do everything they could to keep the cat from getting away and even used fire hoses and paintball pellets. The tranquilizer takes about 15 minutes to take effect. However, the mountain lion was too spooked and continued to move toward the street.
Police said they couldn't take the risk of the mountain lion roaming the streets full of pedestrians. One police officer used a shotgun, and another officer used a rifle, killing the cat.
"It's too bad they had to kill it, but they didn't have much choice," said Mark Leeland of Santa Monica. "If they didn't shoot it, that lion could have killed somebody."
Many people felt that police overreacted.
"All he wanted was to get out of here. He didn't want to hurt anyone, he would never have killed somebody," said Jennifer Conrad, a Santa Monica-based veterinarian who specializes in big cats.
"We have to protect animals and not kill them," Conrad said. "We're in their backyard more than they're in ours."
Police said they can't remember the last time a mountain lion was in downtown Santa Monica. Wildlife experts think the cat may have come from the Santa Monica Mountains in search of food.
It was earlier reported that it was a baby mountain lion, but wildlife experts think the mountain lion was a young adult, about 3 years old and weighing about 90 pounds.
Society for the Prevention of Cruelty to Animals said in a statement that hosing down the animal or shooting it with pepper balls only made the animal more frenzied and urged police to revise the way they handle these types of situations.
A necropsy will be performed on the animal, and some biologists took a piece of its hair to determine if it is related to other mountain lions that they are tracking in the Santa Monica Mountains.