They call themselves names like "King Shizz" and "Gun Smoke Poke," and rap on the Internet about blasting their guns, dying young, and killing their rivals. As a loud bass thumps and an unseen keyboard plays an ominous melody, a half-dozen young men on Castlegate Road in Dorchester jostle for the camera's attention.
"We've got guns that'll [expletive] blow your shoulders back," they rap.
The three-minute video is one of two posted on the Internet featuring teenagers who say they belong to Castlegate and Morse Street, two notorious Boston gangs whose members often turn up in police reports about shootings around the city. Now, the gangs appear to be staking out new turf with their work, which is appearing on the popular video-sharing website YouTube, alongside videos of celebrities, sports highlights, and amateur pranks.
One of the men in the video, a 19-year- old Morse Street resident who identified himself only as Millz, said the rappers are merely trying to launch a musical career online and grab the attention of hip-hop producers.
"We're just rapping," he said in an interview on Castlegate Road, a street off Blue Hill Avenue that is no more than two football fields long and is lined with attached low-rise brick buildings. "That's all it is."
But among their rap's most rapt listeners are Boston police officers, who say the videos may help them identify gang members. If any of the men in the video should appear at an arraignment on a weapons charge, police said, they could use the video as evidence of affiliation with a gang.
"I think it's fantastic," said Police Superintendent Daniel Linskey. "If we can play a video for a judge that shows they're involved with criminal activity, that helps us, and bodes well when we go for dangerousness hearings. We like to use these videos to use their own words against them."
The participants in the videos, all young men who appear to be in their teens, rap about their allegiance to Castlegate and their hatred of rival gangs. In one video, they curse about Dorchester's Wainwright Park and Crown Path, a Dorchester neighborhood, whose names have also been adopted by gangs.
Linskey, who said some of the men in the video are gang members and others could be hangers-on, said he did not know whether the videos had sparked violence between gangs.
Since July 14, about 16 people have been shot in the area of Castlegate Road and Morse Street, according to an internal police document.
The shootings involved associates of the Castlegate, Crown Path, and Morse Street gangs, according to the document, which also warned of possible retaliation because of a perception on the streets that Crown Path was responsible for recent shootings in the Castlegate area.
To some community activists, the videos are dangerous symbols of a culture of violence that is reemerging throughout the city, a sign of the drastic effect of death and mayhem on the young people who live here.
Emmet Folgert, executive director of the Dorchester Youth Collaborative, said it was alarming to see gangs challenging other gangs at a time when gunfire is plaguing city neighborhoods.
"When famous rappers are feuding in their lyrics, it's just a way to sell records," he said. "But these kids saying stuff like that on YouTube is very dangerous. . . . We've got to be aware of what we're dealing with. We're dealing with a gang problem."
But other people who work with gangs say the video was an understandable reaction of young people who constantly witness violence.
"What else do we expect to hear from our youth when they are plagued every day with violence that is destroying our city?" said Talia Rivera, a street worker with the Boston TenPoint Coalition. "The youth in the city of Boston are experiencing death, violence, and guns. It's very hard for them to rap about anything else."
Rivera said she is worried police could brand someone a gang member simply because he appeared in the video.
"There is freedom of speech," she said. "I can say I don't like kids who are Wainwright, but that doesn't mean I shoot kids from Wainwright."
Millz, who said he appeared in one of the two videos, which was filmed in front of Dorchester Pizza and Grill on Washington Street, said he and his friends are trying to launch their own hip-hop label, Black Beam Inc. He said they are using YouTube to attract attention, a path taken by many fledgling musicians.
He said the insults hurled at other gangs are meant to entertain listeners in the same way that rival professional rappers, such as Ja Rule and 50 Cent, do with their lyrical jousting. He did not mention the lyrical rivalry between Tupac Shakur and Notorious BIG that preceded the shooting deaths of both rappers.
"There ain't no beef with nobody," Millz said. "In the industry, you gotta say [expletive] you don't really mean. Give people what they want."
Smiling, he said he had to leave, hopped on his bicycle, and rode down Castlegate toward Blue Hill Avenue.
Maria Cramer can be reached at email@example.com.