A 4-year-old boy was killed Sunday night in a single vehicle crash in Assumption Parish when his aunt’s car careened off the road and struck a culvert, State Police said Monday.

Toniska Willoughby, 22, of Napoleonville, was driving a 2013 Mazda 2 north on La. 308 near the La. 70 spur about 9 p.m. Sunday when her car went off the road and into a ditch, striking a culvert, according to a State Police news release.

Cason Willoughby, her nephew, was pronounced dead at the scene by the Assumption Parish Coroner’s Office.

Cason was sitting in the front passenger’s seat but was not properly restrained, with only the lap portion of his seat belt buckled, State Police said.

Toniska Willoughby was taken to Our Lady of the Lake hospital in Baton Rouge with moderate injuries. State Police are awaiting the results of a blood sample to determine whether she was impaired at the time of the crash, according to the news release.