The Friday attack on two Chinese students at Bok High follows an incident in May where an Asian teenager wearing a school shirt was chased and punched on the street by a group of about 15 African Americans.

In the earlier case, which occurred May 4, a 16-year-old boy who attended Bok was attacked as he walked through the neighborhood near 15th and Morris with his girlfriend. He escaped into the South Philadelphia branch of the Free Library, and the staff quickly locked the doors to bar the assailants from following. The group fled when police arrived.

"The person being attacked ran into the library for safety," Sandra Horrocks, the library system's vice president for communications, said at the time of the incident. "The library staff did shut down the building to make sure the staff and everyone [inside] stayed safe."

She said then that the staff called the Commission on Human Relations "because there seemed to be some racial issue involved." Neither the state nor city human relations commissions had a record of having received such a call in May.

On Monday, school officials investigating the Friday attack said early reports indicated the incident occurred on "freshman hazing day," and that race was not a motivating factor.

Principal Larry Melton said Wednesday night that the incident at the library was never reported to the school. He was asked if knowledge of that assault influenced his view of whether the Friday attack may have been racially motivated.

"I can understand how people with certain interests might want to connect dots to make that point," he said. "I'm remaining open to the whole situation. I'm not going to make any judgments and say that we don't have a problem at our school or that we do have a problem."

According to Philadelphia police, the library incident occurred at 5:27 p.m. May 4. The Asian boy, whose name was not released because of his age, was approached near the library by 15 African American males, all juveniles.

One said, "Are you from Bok?" The assailants then began to punch him.

The victim told police he believed he was attacked because of the school logo on his shirt. Police said at the time that they did not think the incident was racially motivated.

Tensions have been high in the neighborhood since December, when 30 Asian students were assaulted by groups of mostly African American students at South Philadelphia High. That incident was racially motivated, authorities have said.

On Friday, the two Chinese students, both freshman, were kicked and punched by a large group of African American students, according to city school district and police accounts. Both victims required hospital treatment.

A 14-year-old boy was charged with assault.

No other "Freshman Day" attacks were reported, at Bok, Edison or Washington high schools, where Gallard said officials learned that some students had designated Friday as a time to haze ninth-graders.

Melton said on Wednesday that the staff was interviewing students to try to determine the motivation behind the assault.

"What's important to me here is I had two of my students injured," he said. "Any time a student of any group or ethnic group is injured, I'm seriously concerned about it. ... We're going to get to the bottom of this."

Earlier this week, Melton said he had warned students via a public-address announcement that no trouble would be tolerated. He also left a recorded phone message for Bok parents on Friday morning before the incident.

The incident occurred on the sixth floor of the school at Ninth and Mifflin Streets. The two students, one 14 and one 15, were walking to class when the 15-year-old was attacked by about 10 students. The 14-year-old attempted to help his friend, and was then attacked himself.

Contact Inquirer staff writer Jeff Gammage at 215-782-3146 or jgammage@phillynews.com.