Transcript for Arrest made in stabbing death of UCLA student
- News of an arrest in the brutal act of random violence in Los Angeles. So UCLA grad student stabbed to death while working alone in a furniture store in the middle of the afternoon. The suspect then seen leaving by a back door on surveillance tonight.
He's now in custody. And what we've now learned. Here's ABC's Kaylee Hartung.
KAYLEE HARTUNG: Tonight, the suspect now in custody for the gruesome murder of UCLA graduate student, Brianna Kupfer. One of three random killings just 72 hours apart. Raising urgent concerns about the homeless crisis in America.
Kupfer's accused killer, Shawn Laval Smith, who was out on bail has a lengthy arrest record in California and the Carolinas-- including vandalism trespassing and weapons charges. Smith allegedly stabbing the 24-year-old in the middle of the day at the furniture store where she was working alone. Seen in this surveillance video just minutes after the murder.
Kupfer's heartbroken father in shock.
- You don't want to hear it, you want to not believe it.
KAYLEE HARTUNG: That same day Los Angeles Police say another homeless man, Kerry Bell, struck 70-year-old nurse Sandra Shells in the face at a bus stop. Her skull fracturing as she hit the ground.
- It's saddened. It's saddened to hear, you know? Getting ready to retire and this is what happens.
KAYLEE HARTUNG: Police found Bell-- who's been arrested previously in several states-- sleeping a short distance from the scene of the attack. And two days later as a speeding New York City subway car approached the platform. Police say Simon Martial-- who has a history of mental illness and criminal behavior-- pushed financial manager, Michelle go to her death.
The city's new mayor under fire for rising crime in the subway. After initially suggesting the safety concerns were merely a perception. Attending a massive vigil for Go in Times Square and now admitting he himself does not feel safe underground.
- On day one I took the subway system, I felt unsafe. I saw a homeless everywhere.
David, as this memorial to Brianna Kupfer has continued to grow, police say they found the suspect just about 15 miles from here at a bus stop. And according to the LAPD over the past year about 10% of homicides in this city have had a homeless suspect. David.
- Just a horrific story. Kaylee Hartung tonight. Kaylee, thank you.
This transcript has been automatically generated and may not be 100% accurate.