"We have a suspect in custody, we believe that it's a suspect," San Francisco Police Chief George Gascon said.
Gascon says his department has put a tremendous amount of resources into the case.
At 8 a.m., two officers walking on 31st and Judah streets near the Muni metro tracks in the Sunset District spotted a man who fit the attacker's description.
"He was out on the street as they were patrolling; he went willingly, there was no incident," Sgt. Wilfred Williams said.
Police believe 30-year-old Bobby Brown stabbed Rachel Haynes-Brown twice in her side Monday on Muni's J-Church line. She and her girlfriend were on their way to City College.
"I remember this guy walking past me with black shoes hanging from his neck," Haynes-Brown said.
Haynes-Brown, 24, is recovering physically; the emotional healing will take some time.
"I'm shocked and everything's just overwhelming," she said. "Because, you know, people don't think that they're going to wake up in the morning and get stabbed randomly. So, it's just really shocking and a little kind of scary."
Police are trying to figure out if the man who stabbed her is the same one who stabbed an 11-year-old boy on a Muni bus in September.
Supervisor Bevan Dufty told ABC7 he is now pushing the new police chief to do something he says the former police chief would not implement -- an agreement with the city signed seven years ago that officers would routinely ride Muni.
"I kept saying, 'You're a paramilitary organization, how can you tell me you can't get police officers to ride the system,'" Dufty said.
San Francisco police are now analyzing which lines have the most crime.
"We have very limited resources and we have to make sure we put the right officers in the right place at the right time," Gascon said.
Brown was detained for the stabbing in September but he could not be identified by the witness and was released for lack of evidence.
