Be careful what you Tweet -- it could get you killed.

Police say an online war of words spilled over into the streets of Harlem, where a college student studying to become a nurse was gunned down after a testy exchange of messages on Twitter.

According to a report in the New York Daily News, childhood friends Kwame Dancy and Jameg Blake, both 22, engaged in a verbal crossfire on the microblogging site that wound up with Dancy dead and Blake charged with killing his longtime pal.

Angry messages exchanged by the pair on Twitter could prove crucial to Blake's murder trial, the newspaper reported.

The men are said to have fallen out over a girl and become increasingly hostile to each other in the days before the shooting.

Hours before his death, Dancy posted the following message, interpreted by some as directed at Blake: 

"n***** is lookin for u don't think I won't give up ya address for a price betta chill asap!"

According to the criminal complaint, a witness later saw Blake shoot Dancy on the street on Dec. 1 near his home in Manhattan's Harlem section -- the victim of a shotgun to the neck. Dancy was pronounced dead at Harlem Hospital. 

Blake was arrested two days later and charged with second-degree murder and first-degree manslaughter. 

He has pleaded not guilty to the charges and is being held without bail pending his next court appearance on Feb. 2. Attempts to reach Blake's attorney were unsuccessful.

Dancy's mother, Madeline Smith, said she was shocked that the pair's online arguments could have played a role in her son's death.

"That's not a reason to shoot somebody," she told the News. "That's crazy. I don't know what's going on with that Twitter thing."

Smith said her son's dream of becoming of a nurse had been "snatched" from him.

"They were good friends, that's the sad part about it," Smith told the newspaper. "Obviously, I didn't know him like I thought I did. I just want to ask him. 'Why? How could you?'"

Smith said her son was training with the Visiting Nurse Service of New York after taking a semester off from Manhattan Community College. He had planned to return to school to get his degree, she said.

"They've been friends since they were kids," Smith continued. "Kwame would often try to help when [Blake] was going through stuff -- and this was his thank you?"