Heather Phares, 22, an off-duty Midlothian Police Department officer, was critically injured, airlifted to hospital, after her pickup crashed into the back of a tractor-trailer on State Highway 287 Midlothian.

An off-duty Midlothian police officer was seriously injured in a crash Thursday.

According to the Midlothian Police Department, the officer was traveling along state Highway 287 when her truck crashed into the back of a tractor-trailer carrying a load of steel.

The officer, 22-year-old Heather Phares, had to be extricated from the damaged vehicle and flown by air ambulance to Parkland Memorial Hospital in Dallas. She suffered traumatic head injuries in the crash and is in critical condition.

Phares was the only occupant of the truck and was driving home after working a special assignment with the local school district, the department said Friday afternoon.

Phares has been with the department for almost two years.

UPDATE: Officer Heather Phares died of her injuries, at a hospital in Dallas, on 04/21/14.