Shawn Laval Smith, 31, is considered “armed and dangerous,” the Los Angeles Police Department said in a tweet, warning people to call 911 instead of approaching him. Smith has been in Pasadena, Santa Monica, West Hollywood, Covina, San Diego, San Francisco, and several other locations around Southern California, according to a wanted poster. Police urged residents to pay special attention at bus stops and train platforms as “he is highly likely to be using public transportation.”Officials and the community are offering a $250,000 reward in the case.Brianna Kupfer, 24, was stabbed with a knife before her attacker fled down the back alley of the store last Thursday afternoon, the LAPD said Tuesday.Just after 1:30 p.m., Kupfer, who had been working alone in the store, texted a friend that someone there “was giving her a bad vibe,” Lt. John Radtke of the LAPD said at a news conference. The person receiving the text didn’t see it immediately, he said.A customer entered the store about 15 minutes later and found Kupfer “on the ground, lifeless, covered in blood,” Radtke said. The attacker was not known to the victim and was a random walk-in to the store, LAPD said. Police have not publicized the name of the store but said it’s located in the 300 block of North La Brea Avenue. The victim, from Pacific Palisades, was enrolled in extension courses at UCLA, the university said. “Brianna was a smart, funny driven and kind soul who only wanted to better herself and her community on a daily basis,” her family said in a statement read by a city council member at the news conference. “While she could be shy at times, she lit up any room she was in and strove to elevate everyone she met so they could be better versions of themselves.”Her father, Todd Kupfer, told Fox News he didn’t know why she was in the store alone.He said Brianna was curious about the world and competitive with her three siblings. “She was a great role model, she was very, very caring,” her father said. “I’m so proud of what she’s accomplished and where she was going.”The city is expected to offer a $50,000 reward for information leading to the suspect’s arrest and prosecution, and people in the Westside community donated more than $200,000 for information leading to the persons’ arrest and conviction, City Council member Paul Koretz said. The seemingly random and senseless killing of Brianna Kupfer “has shaken and shocked our community to the core,” Koretz said. “We will find this vicious criminal, we will arrest him and we will get him prosecuted to the fullest extent of the law,” he promised.An “intensive investigation” is ongoing “and will continue until this man is identified and brought to the criminal justice system,” LAPD Chief Michel Moore said. “Let me commit to you that investigatively, we’re pulling out every stop” to solve the crime, Moore said. CNN’s Cheri Mossburg and Sarah Moon contributed to this report.