A father and son were shot while riding motorcycles on the I-93 Expressway Southbound near Exit 12 in Boston's Dorchester neighborhood.
One victim, a 54-year-old Raynham man, was transported to Tufts Medical Center with serious injuries not believed to be life-threatening.
The other victim, a 32-year-old East Taunton man, was taken to Boston Medical Center and is in critical condition.
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A suspect fled in what has been described as a red Jeep Renegade, according to Massachusetts State Police.
The vehicle was found in Dorchester on Sunday night, but no arrests were made. Police say the vehicle is in a facility for processing and the public's help locating it is no longer required.
The investigation remains underway.