Two boys were cut by razor blades that police said were deliberately placed near a playground in San Diego.

Cassie Padilla's two sons were injured Wednesday in Bonita Cove Park. "They both stepped on razor blades," Padilla told ABC affiliate station KGTV, speaking of her sons aged 7 and 15. "It's pretty crazy. It's really bad."

A razor blade was "actually embedded" in the foot of the younger boy, Lt. Paul Phillips of the San Diego Police Department told KGTV. "Paramedics were able to pull the razor blade out," Phillips said.

Razor Blades Found Taped to Playground Equipment

The 15-year-old had a superficial wound, according to authorities.

Police searched the park with metal detectors and found at least 19 razor blades. "It's either a sickness or someone who's got an evil mind," Phillips said.

This is the fourth time in about a year that razor blades have been planted in the Bonita Cove Park.

Similar incidents have also occurred across the country.

Three-year-old Madden Jenks was climbing monkey bars at Millennium Park in East Moline, Illinois, last month when he was cut by a razor blade.

"He said, 'Ouch.' And then he started bleeding," his mother, Sally Jenks, told ABC affiliate station WQAD-TV.

The boy's parents found razor blades tapes to the bars, swings and climbing wall at the park. "We looked and they were everywhere. The razor blades were everywhere," Jenks told WQAD.

Razor blades were also found at Eaton Park in Delaware County, Pennsylvania, on April 1. No one was injured. "I just felt sad that someone would do that to this nice park," a young boy at Eaton Park said.

The razor blade cases appear to be unrelated, according to police.