NASHVILLE, Tenn. (AP) — A Tennessee convict on lawn mowing duty sexually assaulted and strangled a female corrections administrator before escaping prison grounds on a tractor, authorities said.

The Tennessee Bureau of Investigation said Friday it has received 250 tips but there have been no credible sightings of Curtis Ray Watson since he escaped the West Tennessee State Penitentiary two days ago.

Watson was discovered missing about 11 a.m. Wednesday, several hours after he was seen near the house where 64-year-old employee Debra Johnson lived on prison grounds, according to an affidavit from the TBI filed Thursday.

Watson, 44, had been released temporarily for mowing duties at 7 a.m. earlier that day, and had access to a golf cart and a tractor. As a “trusty” at the prison, he was allowed to use the equipment and had to wear a reflective vest while working on prison grounds, the affidavit says.

Phone records show Johnson was talking on the phone at 8:10 a.m., just 20 minutes before corrections workers saw Watson in a golf cart at her house, according to the affidavit. He drove away from the prison sometime between 9 and 10 a.m. on a tractor, the affidavit says.

When Johnson didn’t show up for work, co-workers discovered her body at her home at 11:30 a.m., according to the affidavit, which notes that agents found a cord wrapped around Johnson’s neck. The medical examiner declared her death a homicide by strangulation, the affidavit says.