Anthony Taylor Jr. was killed over the color red.

The 20-year-old Bloods gang member was partying with friends past midnight, hanging out on the corner of Guilford Avenue and East 22nd Street, a red bandana tied to his belt.

But police said a member of the Young Gorilla Family, which claimed the Barclay neighborhood as its own, had warned Taylor he was not allowed there wearing the signature color of the rival Bloods.

The two men fought, as they had in the past, but this time another Young Gorilla retrieved a 12-gauge shotgun and, according to police, ended the long-simmering feud with a single blast. The gunman then fired on Taylor's best friend, Adrian Holiday, a hotel valet and Baltimore County Community College student who was not involved in a gang.

Both died on the corner, across the street from a branch office of the Maryland Division of Parole and Probation.

On city streets long beset by violence, last September's double slaying presaged a rising threat.

Though Baltimore crime has long been fueled by loosely formed neighborhood crews, increasingly organized groups have found new reasons to kill - such as showing a red bandana on the wrong street. Now, those who police the city and schools, as well as the jails and prisons, are fearful of the potential growth and impact of these gangs, which are more brazen in their crimes and quick to pull a trigger.

Seeds of that growth were planted about six or seven years ago, law enforcement officials believe, when out-of-state gangs began targeting Baltimore - taking advantage of the city's thriving drug trade and proximity to Interstate 95. Often, they made inroads by recruiting within the state's prison system.

Today, statistics can be hard to come by and much of the evidence is anecdotal, but police say they already have identified about 2,600 known or suspected members of street gangs, including 400 Bloods, 100 Crips, and a few dozen members of Mara Salvatrucha, or MS-13 - a Latino gang that has gained a prominent and violent foothold in the Washington suburbs.

Baltimore gang members mimic the mannerisms, coded language and secret hand signals of their counterparts in Los Angeles and other cities; court documents in a murder investigation even indicate that L.A. gang leaders have sought tribute money from members here.

Most of the gangs' violence-fueled crimes have been restricted to pockets of Baltimore where the drug trade flourishes. But police say that gang initiation rites - such as stealing cell phones - have triggered crime sprees in the Inner Harbor and other areas, while targeting tourists or residents of bustling neighborhoods.

Last summer, for example, about 20 suspected gang members accosted four high-school boys visiting the Inner Harbor from New Jersey, robbing them of money and cell phones, police said. During July 4 festivities at the Inner Harbor, police also rushed to help an elderly woman in a wheelchair who was being harassed by a crowd shouting "L-Up and Blaat," gang slang used by a Bloods offshoot.

In another incident last year, a gang operating near downtown Baltimore required new members to rob people, police said. The initiation rite had to be witnessed by other gang members, who in turn had to rob someone else to build trust within the gang.

"Do you know a wave that sets off?" said Deputy Police Commissioner Frederick H. Bealefeld III. "Do you know how many robberies we had? There were a ton."

He added, "The gangs don't achieve stature by academic achievement. They don't achieve stature by goodwill. Their identity is sewn into violence. They are fueled and funneled by the drug trade."

Law enforcement officials are struggling to keep ahead of this new problem in Baltimore. City prosecutors wanted state lawmakers to craft tougher anti-gang measures modeled after federal conspiracy statutes, but were disappointed with watered-down legislation that came out of the 2007 General Assembly session. Authorities, though, are still debating among themselves what constitutes a gang and what kinds of crimes can be attributed to them.

Baltimore authorities say it is difficult to link the new phenomenon with a spike in violent crime, because comparative data from previous years is not available. But based on experiences on the street, they fear an escalation of gang influence as neighborhoods are demarcated by graffiti and children are recruited as early as middle school.

Baltimore school police have identified 33 gangs, including at least nine Bloods sets and three Crips sets, in the school system. Children as young as 12 years old have affiliated with gangs, school police officials say.

The same trend is occurring in other cities. Cleveland police just finished a yearlong drug investigation and arrested four members of the Compton Crips, a California-based gang. The city has also seen a spike in activity from branches of a Chicago gang.