WINFIELD TWP — A31-year-year old Cabot woman was killed late Sunday night when her speeding car slammed into a tree along Route 356, authorities said.

Rhonda Heckert was pronounced dead at the scene about 11:45 p.m. Butler County Deputy Coroner Chuck Lewis said it appeared Heckert died of massive head injuries.

State police said the woman was not wearing a seat belt.

An off-duty municipal police officer on the way to work apparently was the first person to drive upon the crash, which was loud enough to wake nearby residents.

"It was a pretty violent crash,"said Chief Sean Smith of the Winfield Township Volunteer Fire Company.

Police said Heckert, about 11:25 p.m., was southbound on Route 356, about one-quarter mile south of Associated Ceramics, when she lost control of her 2007 Chevrolet Cobalt.

Investigators suspect the car was traveling at "a high rate of speed,"according to a police news release.

The car crossed into the northbound lane and then went off the road, hitting the tree with its front passenger side near the quarter panel.

"The passenger side was pushed in about 3 feet,"said Lewis said, noting the car sustained major damage.

Investigators noted there appeared to be skid marks left by the car before it went off the east side of the road.

"It was a little hazy last night,"Smith said, "but the weather shouldn't have been a problem. The road was dry."

State police accident reconstruction specialists are assisting in the investigation.

Lewis said he did not immediately know if there would be an autopsy.