Evaughn-Sha Walters pleaded guilty to homicide by vehicle charges on Thursday.
Walters was racing Shone Santiago down Route 422 in West Pottsgrove Township, Pa., back in February when Santiago crashed.
Both of Santiago's passengers, including a pregnant woman, were killed.
Detectives estimate both men were driving between 121 and 137 miles per hour.
Santiago has yet to enter a plea.
Walters will be sentenced next month.
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