The operator of a Harley Davidson motorcycle was seriously injured in a collision on Bells Ferry Road Thursday evening. A passenger on the motorcycle was also treated for injuries.

According to a press release from Officer Neil Penirelli of the Cobb County Police Department Dylan Threewitt, 25, of Canton, was injured when his motorcycle was disabled and stopped in the left northbound lane of Bells Ferry Road just south of Shallowford Road.

The incident occurred at around 9:30 p.m., and is being investigated by the Cobb County Police Department’s Selective Traffic Enforcement Program (S.T.E.P.) Unit.

Investigators report that a Toyota Sienna driven by Rye Pak, 58, of Acworth struck the disabled motorcycle from behind, ejecting Threewitt into the roadway where he was struck by another northbound vehicle. The vehicle that struck Threewitt stopped briefly, but then drove away.

Threewitt was taken by ambulance to Wellstar Kennestone Hospital with critical injuries, and his passenger, Kayli McGaha, 25, of Marietta was also taken to the hospital with non-life-threatening injuries.

Pak, the driver of the Toyota, was not injured.

The press release states, “Witnesses described the second vehicle as a small dark colored Sport Utility Vehicle (SUV). Investigators are requesting anyone with information about this hit and run vehicle to contact the Cobb County Police Department’s S.T.E.P. Unit at 770-499-3987.”

What is the STEP Unit?

The STEP Unit, which investigates serious or fatal traffic crashes, is one of the Cobb County Police Department’s Special Operations units, and  is described on the web page of the Cobb County Police Department as follows:

“The Selective Traffic Enforcement Unit is responsible for investigating all fatal traffic crashes, enforcement of traffic laws in those areas which analysis indicates an elevated amount of crashes. They are also responsible for the administration and execution of the Motor Carrier Safety Assistance Program. They also take part in special security details, and investigate crashes involving Department vehicles when requested.”