LINCOLN, Neb. (AP) — A Lincoln man found dead in his car in January died of carbon monoxide poisoning.

Lancaster County Attorney Joe Kelly announced Friday that 28-year-old Craig Baxter died of carbon monoxide poisoning, but it wasn’t clear if it was accidental or intention.

Baxter was reported missing Jan. 4 after he failed to show up for his first optometry rotation at Omaha Eye & Laser Institute. He was last seen leaving his sister’s Lincoln home earlier that day.

He was found dead inside a car in an open garage on Jan. 10 in Lincoln.

Baxter was in his fourth year of studying optometry at Southern College of Optometry in Memphis, Tennessee. He was from North Platte, Nebraska.