Seventeen years after race riots left the streets of Crown Heights bloodied, tensions are rising again in the neighborhood restlessly shared by Orthodox Jews and blacks. First, a black man was badly beaten on a Brooklyn street. Weeks later, a Jewish teenager said he was attacked by two young blacks while riding his bicycle, and angry Jewish residents took to the streets with signs saying "Jewish blood is not cheap!" and "Every Jew a .22." And along the way, the district attorney accused an Orthodox Jewish street patrol of vigilantism and compared the group to street gangs like the Bloods and Crips. The strife has revived painful memories of the 1991 riots in the neighborhood, which is home to about 15,000 Orthodox Jews and more than 130,000 blacks. As summer approaches, leaders from both sides are braced for trouble. "One small incident could escalate into something beyond our grasp," warned Richard Green, head of the Crown Heights Youth Collective, a group he said inspires the races "to interact instead of react." The group was started after the 1991 riots that exploded after a black child was accidentally struck by a station wagon in the motorcade of a Jewish spiritual leader. The 7-year-old boy, who was pinned under the vehicle, later died of his injuries. In the ensuing unrest, which lasted three days, a rabbinical student was mortally stabbed by a black mob. To quell fears of new unrest, NYPD Commissioner Raymond Kelly visited Crown Heights earlier this month and stepped up police patrols. Officers are also perched atop a tower, keeping 24-hour watch over the world headquarters of the ultra-Orthodox Lubavitch movement. In addition, two Jewish patrol groups claiming hundreds of volunteers cruise the streets by foot and car. "It's a very delicate situation in Crown Heights, a bubble of tension," said Geoffrey Davis, a longtime black resident. Queens borough District Attorney Charles Hynes has convened a grand jury to probe the April 14 assault on Andrew Charles, a 20-year-old son of an NYPD detective. He told police that a man on a bicycle sprayed him with mace while another man stepped out of an SUV, struck him with a wooden object and drove off. Police have released a photograph of a 25-year-old member of the local street patrol group, the Shmira, who is wanted for questioning in what Hynes calls "an unprovoked attack." Police suspect the attack followed reports that black youths had pelted neighborhood homes with rocks. In May, residents say stones were hurled at a school bus carrying Jewish children. Charles' mother is accusing police of having "a double standard," noting that they've made no arrest in her son's case while two black teenagers were quickly charged with beating and robbing a Jewish 16-year-old riding his bicycle several weeks ago. "My son's suspect is still at large almost a month after he was brutally assaulted!" said Charles' mother, Wendy Craigg. The prosecutor's office said it could not discuss the details of a case under investigation. However in April, Hynes told The Jewish Week: "You can't have a group, whether it's the Bloods, Crips or Shmira, acting like vigilantes." The prosecutor later tempered his remarks in a letter to the newspaper, explaining that he "didn't intend to suggest that the Shmira were capable of the violence which is the signature of street thugs like the Bloods and the Crips." However, the prosecutor said, when there's a group "like Shmira, which may have been part of this unprovoked assault, I ... intend to do everything possible to find out where the truth lies." In Crown Heights today, the truth depends on the speaker. Members of the Shmira, which means "to watch" in Hebrew, are quick to show that they protect both blacks and Jews. In early May, a Jewish man standing in front of the Lubavitcher headquarters was surrounded by four black men who confronted him, cutting his hand. The Shmira chased down the four and called police, according to Yossi Stern, Shmira's director. In another recent incident, Stern said, a young black woman leaving the subway was confronted by a knife-wielding man who forced her into an apartment building, where he tried to remove her clothing. Her screams were heard by a resident of the building - a Shmira member who pursued the assailant and called emergency dispatchers. But NYPD spokesman Paul Browne said that the Shmira "does not cooperate with police like other community watch groups who are our eyes and ears." He said the group has not supplied police officials with the names of its members, as do other such groups in the city. Still, the current tensions do not even begin to approach 1991 levels. Reported crimes in the precinct that includes Crown Heights have dropped steadily since then - 77 percent in the past 15 years. And Green says community residents now have an outlet: Various groups like his formed after the riots to encourage common activities, from sports to the arts, while bridging differences to avert future clashes. "Race relations are absolutely better than in the '90s, when we were like two ships passing in the night, picking up each other's radar," said Green, 60, a Crown Heights resident and history professor at the City University of New York. While the latest violence is creating unnerving flashbacks, it's also bolstering the coalition that blacks and Jews forged after the riots. On a sunny Friday afternoon, Jewish families hurried to prepare for the Sabbath, pushing along baby carriages while walking alongside black neighbors and shopping in the same stores. Stern was driving through the neighborhood when suddenly, he stopped his car to greet a friend - Davis, who gave the Shmira official a big smile and told him that he was on his way "to pick up a Torah for myself."