It wasn't all that long ago that many Philadelphians thought of gun violence as the city's biggest problem.But in the span of one disturbing week, out-of-control teens have topped the list of local public-safety concerns.On March 26, six teens brutally attacked Starbucks manager Sean Patrick Conroy on an underground Center City SEPTA concourse. Conroy, 36, died from a fatal asthma attack brought on by the beating.Police charged five Simon Gratz High School students as adults with Conroy's murder, which investigators said was unprovoked. The hunt continues for the sixth person involved.Conroy's death unsettled local commuters, but the incident seemed like an anomaly.That all changed on Wednesday night, when police said Tyesha Tazwell, 24, was attacked after she exchanged words with a group of 12 youths - ranging in age from 16 to 20 - near an underground concourse between SEPTA's underground lines and the Gallery Mall at 8th and Market streets, just five blocks from where Conroy was killed.Tazwell survived, but police said she lost a tooth, had a chunk of hair ripped from her skull and suffered vision loss and lacerations to her head. SEPTA police arrested five of her attackers.In the minds of many Center City commuters, the incidents left them feeling uneasy about sharing trains and subway platforms with youths capable of such deplorable violence."You've got to watch kids now. You've got to be prepared," said Tony Sessoms, 35, who was waiting at the 8th and Market subway station yesterday afternoon with his two young daughters.The young people are lashing out, doing the wrong things . . . this city used to be one of brotherly love, but it has no brotherly love anymore."Lucy Leto, 52, who was at the same stop, said she doesn't at all feel safe riding local trains. "It's the just the way kids act today," Leto said.Keenan Jones, the co-founder of Black Entrepreneurs and Rap United Together, a local entertainment company, said he worked with many of the teens involved in Wednesday's attack.He said the teens lost a friend and fellow group member to suicide on Tuesday. Jones said they didn't know how to deal with their loss, which is why they lashed out when they had words with Tazwell."They were not some thugs who went downtown to attack people," he said."Nothing justifies that type of act," said police spokesman Lt. Frank Vanore. "A lot of these kids have a video-game mentality where they think they can just start over without paying consequences."