Police investigate the residence of a teenager arrested in connection with the recent Petworth neighborhood attacks. (Linda Davidson/THE WASHINGTON POST)

D.C. police said Saturday that a fifth person who was suddenly attacked from behind in the Petworth neighborhood had come forward, and a man arrested Thursday was charged with both the fourth and fifth assaults.

Michael Davis, 19, a suspect in five attacks over a three-day period, made his first court appearance Saturday in D.C. Superior Court and was ordered held without bond. Standing in a white jumpsuit and shackles, he did not speak during the hearing. He was charged with two counts of assault with intent to kill while armed.

A number of family members burst into tears when he was ordered back to jail, but they declined to comment afterward.

Davis has not been charged in the first three attacks in the series, including the one Tuesday evening that killed Gary Dederichs, a 66-year-old Denver man. Dederichs was found fatally beaten in the 800 block of Emerson Street NW about 6 p.m. The medical examiner told police Dederichs was killed by blunt-force trauma to the head, with injuries consistent with those caused by a claw-style weapon or hammer, according to court records released Saturday.

Police said Saturday they found a small black sledgehammer wrapped in a white plastic bag in an alley alongside 926 Emerson Street NW, a block from where Dederichs was slain and three doors down from Davis’s residence. An affidavit by homicide Detective Gabriel Truby said that the bag and the sledgehammer were found Thursday and that both appeared to have blood on them.

About nine hours after Dederichs was found, a 53-year-old man was discovered in the 4800 block of Georgia Avenue NW with a fractured skull and multiple facial fractures, police said. Truby wrote that this attack occurred less than 500 feet from the house where Davis lived with his grandmother.

Later Wednesday, a 37-year-old woman was found in the 5600 block of Ninth Street NW with a fracture in the back of the skull. In the Dederichs slaying and the two subsequent attacks, nothing was taken from the victims, police said.

D.C. Police Chief Cathy L. Lanier held a news conference Thursday to warn people about the sudden and apparently unprovoked attacks in the Petworth area. Police blanketed the area around Georgia Avenue and were on the scene in moments when a 19-year-old woman was suddenly struck from behind around 9 p.m. by a man who had been following her in the 800 block of Gallatin Street NW.

Officers spotted a man nearby who took off running. As they chased him, police said they saw him toss away a backpack. They said they lost him but located him again in the 4800 block of Illinois Avenue NW. A blue and white, horizontal-striped hooded sweatshirt described by the victim was found nearby, Truby’s affidavit states. In the discarded backpack was a hammer with “what appeared to be hair on the claw end,” Truby wrote.

Davis, the brother of NFL players Vernon Davis of the San Francisco 49ers and Vontae Davis of the Miami Dolphins, was arrested.

After Michael Davis was arrested Thursday night, a District man came forward Friday afternoon to report that he had been attacked Thursday, too. He told police he was walking his dog in the 200 block of Ingraham Street NW about 3:35 p.m. when a young man with a backpack approached from the other direction.

The two said hello to each other, the man said. When he turned to look at his dog, he said, he was struck from behind and knocked down. He sustained cuts to his head and upper lip and thought he’d been hit by something more than a fist, Truby wrote. He did not initially report the incident because he was embarrassed and wanted to think about it, he told officers.

The victim went with police back to the scene, where they found blood on the sidewalk and a broken rubberized handle of a hammer, Truby wrote. The victim, whose age was not released, reportedly picked Davis out of a sequential photo lineup. The man said he had not seen any photos of Davis in media coverage.