Police, fire crews and other law enforcement agencies were on the scene at Middlesex Hospital around 10:00 a.m. Thursday.
Local authorities evacuated homes in the neighborhood where the driver lives and notified federal authorities.
Officials said a security guard was taken in for treatment for smoke inhalation, but everyone else in the hospital was safe and accounted for.
The hospital was placed in an "emergency operations mode", hospital officials said. As a precaution, a bomb squad was dispatched to the hospital and surrounding area. The hospital said it is not allowing visitors, except for special circumstances.
Ellam has an extensive criminal history in CT that goes as far back as 2008, according to WFSB. In 2013, a jury found him guilty of attempted strangulation. "I got up, looked out the back window and then I looked at the hospital and that's when I saw the auto in there, and then I saw a guy come running out", he said.
"I heard a noise", witness Gary Mills said.
"I want the public to know that this has been determined to be an isolated incident", he said.
Emergency patients at Middlesex were brought to MidState Medical Center, the Hospital of Central Connecticut and Hartford Hospital until for the time being.