Police are looking for a man who brutally beat and sexually assaulted a 15-year-old girl near a Chicago Public Schools Safe Passage route before leaving her freezing in a stranger's Northwest Side yard.

Michael Klockowski discovered the beaten, bleeding and half-naked girl in the backyard of his Belmont-Craigin home in the 2400 block of North Long Avenue around 8 a.m. Tuesday. The girl had been lying in cold for some two hours, with her pants, a boot and other articles of clothing missing.

"Just opening the door to take maybe a morning sweep of the sidewalks. And to find something like that is just shocking," Klocklowski told ABC Chicago.

Police say the attack happened sometime after 6 a.m. -- before Safe Passage workers are at their post at 7 a.m. -- as she was on her way to catch a bus to her charter school some six miles outside the neighborhood.

The Tribune reports the girl appears to have been hit in the head before the assault. She was found with a pool of blood around her head with more spattered around the scene. Blood was also smeared along the house and over the doorbell, leading officials to believe she was trying to signal for help.

“There was a lot of blood,” Klockowski told the paper. "We've got somebody that's really bad out there."

Police also found a condom wrapper nearby and footprints in the snow. The girl was taken an area hospital in critical condition.

CPS officials deferred the Tribune's questions to police saying the girl wasn't found on a Safe Passage route.

As DNAinfo Chicago notes, the route is just blocks from the Safe Passage route for Northwest Middle School with two more schools -- St. Prosser Career Academy and Hanson Park Elementary School -- nearby.

The attack's proximity to so many schools has left Klockowski unsettled, as he told the Sun-Times:

“I just hope they find the person who did this because there’s so many children in this area, and one can’t help but suspect that somebody might, like this, [capable] of something so violent, might do it again, sometime soon."

Anyone with information is asked to call 312-744-8261.