CHAPEL HILL, N.C. -- The suspect in Thursday’s fire and explosion at UNC-Chapel Hill is undergoing a mental evaluation at a hospital. 

Meanwhile, a professor is also recovering from burns after he tried to put out the fire.

The DA confirms the hospital is mentally evaluating the unidentified suspect.

Meanwhile, a source close to the investigation says the former UNC student will be arrested on arson and assault related charges ad possibly planting an incendiary device underneath the Davie Poplar tree on McCorkle Place.

Professor Dan Reichart tried to put out the fire before it exploded sending him back.

He suffered first and second degree burns on his hands and face.

Before that, campus police were called to the scene after a device caught fire at the base of the Davie Poplar.

Witnesses say police arrested the suspect but he yelled bizarre statements such as "Hail Satan" and "I killed Davie Poplar, now the university will fall."

Shortly after this, Carrboro police located his vehicle and used a device to open it up, but didn't find anything suspicious inside.

Meanwhile, we spoke with the injured professor over the phone.

He says he saw the fire when he tried to put it out.

“I went to the tree and I tried to stomp it out or kick it away from the tree. I was probably there for 15-30 seconds and it accelerated. The flames grew very quickly. And I was getting ready to back away from it and it blew. And it threw me back. I saw the video last night. It looks like it threw me back 20 or 30 feet,” said Reichart.

Professor Reichart says he will have surgery today.

He teaches astronomy and hopes to be back in the classroom as early as next week.