**Warning: The video shown below may be considered disturbing**
OKLAHOMA CITY, Oklahoma -- A Tulsa dentist is accused of killing his girlfriend's 19-month-old son, and prosecutors are using surveillance video to try and prove it.
KFOR reports that Bert Franklin, 35, was charged in the death of baby Lincoln Lewis, who died July 17.
In court, prosecutors showed surveillance video taken in the home of Lewis' mom, Roxanne Randall, the night her baby was fatally injured.
It shows Franklin walking down the stairs of the home with Lewis in his arms. The baby is sitting up and appears to be fine. Franklin is then shown taking the baby into the living room. What happened next isn't shown clearly because the camera was situated in the kitchen.
But detectives say they believe the video shows Franklin slamming the baby headfirst into the floor and then kicking him.
Franklin is then seen carrying the limp baby in one arm as he grabs a piece of pizza from the kitchen.
The baby's mother told police she was home at the time and heard a thud. She came downstairs and said Franklin told her the sound was him throwing a ball to the dog. She said the baby was on the couch with pillows around him, and Franklin said he was sleeping.
They put the baby to bed, but when Randall tried to wake him hours later for his bottle, she discovered his eyes were open and he was having a hard time breathing.
He was taken to the hospital and later died.
Franklin's attorney, Scott Adams, said he wasn't surprised by the video and that it goes along with what Franklin said happened.
“But there’s really nothing on the video that surprised me. I mean it is what it is. And again, Dr. Franklin has told us there was a dog in there and any actions he had was towards the dog and I believe him,” said Adams.