Graphic Warning: Viewers may find video in this story disturbing to watch

Missouri police are searching for a suspect who was caught on security video beating a senior man with a gun.

Investigators said a man wearing a mask with a skull on it approached a home in St. Louis, Mo. on Friday afternoon, and forced his way inside after a 79-year-old man opened the front door.

Security footage taken from inside the home shows the intruder take off the senior’s baseball cap and press a gun to his head.

“What the hell is this? Get out of here! Get out of here!” the man can be heard yelling before the suspect smacks him across the head with the gun.

The senior is seen stumbling towards a chair in the foyer where he sits down and shouts at the man, “Ow! What’s the matter with you” multiple times as the intruder repeatedly hits the man on the head with the gun.

Moments later, the intruder shoves the man from the chair and onto the floor. The suspect can be seen patting the senior man’s jean pockets as he lies on the ground and says “I don’t have one” repeatedly.

“What is wrong with you?” the senior asks his attacker again. “You’re hurting me.”

Less than two minutes after the incident began, the suspect is seen leaving the home.

Police said the suspect stole the man’s cellphone and a few other items.

Neighbour Yolanda Forest said she found the security video difficult to watch.

“Oh poor man!” she told local television station KMOV. “That is so sad. Wish it was me instead of him.”

The suspect is described as wearing a mask with a skull on it, a tan cap, and a pea coat. Investigators are asking anyone with information to contact the St. Louis Metropolitan Police Department.