CHICAGO (CBS) — Police were investigating Wednesday afternoon after a man was pistol-whipped in a home invasion in Rogers Park.

The incident happened at 10:09 p.m. Tuesday in the 1300 block of West Greenleaf Avenue between Glenwood Avenue and Sheridan Road, police said.

A 22-year-old man was in his apartment with his friend, a 20-year-old man, when they heard a knock on the window, police said.

The older man looked and saw a third man whome he knew, and he went to open the front door. But when he opened the door, he saw the man he did know was accompanied by two men he didn’t know.

The man whom the older victim knew took out a handgun and forced his way along with the other two men into the building and the apartment, police said.

Afterward, the man with the gun pistol-whipped the younger victim inside the apartment, and the assailants took the younger man’s backpack – which contained his personal property – before running off, police said.

The man who was pistol-whipped was taken to AMITA Health St. Francis Hospital in Evanston for an injury to his head, police said.

The older victim told police he had hung out with the man who had the gun before, but did not know his name or anything about him.

The Rogers Park incident happened about an hour after another violent home invasion on the north lakefront six miles to the south.

Around 9:10 p.m. Tuesday, a woman was attacked in her apartment in the Beachwalk Apartments at 420 W. Fullerton Pkwy. in Lincoln Park.

Police said the 32-year-old woman was inside her apartment when she heard a knock on the door. When she answered her door, three men rushed into inside. She did not know the men, and they covered the peep hole while knocking, according to a police source.

A police source said the were all armed with guns and repeatedly slapped and hit her in the head and on her face and hit her in the head with an unknown object. They demanded money, and when the woman said she didn’t have any, one of the suspects put a gun in her mouth and threatened her life, a police source said.

The woman was then forced to lie face down on the bed where she was handcuffed and had her mouth taped shut. The men went on to steal miscellaneous items from the apartment before running off, police said. A police source said they took a ceramic container filled with cash, her purse and wallet and a laptop.

Area North detectives are investigating both incidents. They are not believed to be related.