Meaning?

Hi,
What is the meaning of" easiest collar we've ever made" and "cops" in the following text:
"How did you get onto him?"
"That was the easy part. He walked into the precinct at two o'clock this morning and turned hi m in. Easiest collar we've ever made .I've just come interviewing him."
Decker shot her penetrating look. "After nearly sixteen months the guy walks in and cops to a triple homicides"
Does collar and cop mean arrest and confess respectively?
Thanks