SAN ANTONIO -

A man was critically injured after he slammed into a his windshield during a crash early Friday morning,

The accident happened around 2:30 a.m. on Loop 1604 and NW Military.

Police say the driver lost control of his pickup truck for an unknown reason and crashed into a guardrail. 

Police said he was not wearing a seat belt and the impact caused him to slam into the truck's windshield.

The driver was taken to University Hospital in serious condition with head injuries, police said.