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PHILADELPHIA (CBS) — The driver who hit another car head-on, killing three people, including two Mummers and a newly engaged couple, has been charged with three counts of vehicular manslaughter, according to the Philadelphia District Attorney’s Office. Keith Campbell, 29, who had been stabbed between 15 and 20 times at the time of the crash, was charged Thursday.

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Campbell has been charged with three counts of vehicular manslaughter in the deaths of Dennis Palandro Jr., Joseph Ferry and Kelly Wiseley. Ferry and Wiseley got engaged over Christmas.

The crash happened Wednesday morning at 7th Street and Packer Avenue in South Philadelphia.

Campbell was also charged with one count of aggravated assault, one count of reckless endangerment and one count of possession of an instrument of crime.

As police and the DA continue to investigate the incident, it’s possible additional charges may be filed.

Police also released new information Thursday about the crash.

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Police now say they found a letter inside Campbell’s car.

Eyewitnesses tell police Campbell was driving erratically. Police say he may have stabbed himself.

Couple Engaged Over Christmas Among 3 Killed In Head-On South Philadelphia Crash

They’re not saying what’s in the letter, only that it’s considered evidence.

“We are examining the contents to see how relevant it is to the case,” Sgt. Joe Rossa said.

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Meanwhile, the South Philadelphia String Band is mourning its members killed in the crash.