He came back for deadly revenge — with a hammer.
A hulking, mentally ill man whose mom kicked him out after he became increasingly violent tragically proved her fears right early Saturday, returning to fatally bludgeon her, his younger sister, and a family friend who was in the wrong place at the wrong time, police said.
The newly homeless Bobby Vanderhall allegedly flew into a rage when he came back to find the door to the Hempstead home on leafy Perry Street locked, police said.
“He went to the garage, he obtained a large hammer. It’s called a framing hammer,” Det. Lt. Stephen Fitzpatrick, commanding officer of Nassau County Homicide, said.
He smashed his way inside with the hammer and made his way to the living room, where he found his mom, Lynn, 58 — and started swinging, police said.
Vanderhall’s younger sister, Melissa, 28, and two friends were just upstairs and heard the fatal beating, but could not escape.
“The girls, who were all upstairs, heard what was going on in the living room. As they came to the staircase, Bobby was already coming up after them,” Fitzpatrick said.
One of Melissa’s pals, Janel Simpson, 29, succumbed to her injuries.
The other friend, whose name was not immediately released, survived with a fractured wrist, what police called a defensive injury.
She survived only when Vanderhall, 34, turned again against his sister, allowing her to slip out the door and summon help, police said.
Vanderhall has been charged with three counts of murder and one count of attempted murder.
His sister’s two friends were seen as collateral damage in Vanderhall’s mind, Fitzpatrick said.
“Basically, because they were there when he went to kill his mom and his sister, they had to go,” he said.
Vanderhall has a history of mental illness; twice he’d been taken to the hospital for “emotional issues,” he said.
“It may have some cause in this [crime] but not an excuse for what he’s done,” the Detective Lieutenant said.
Twice previously police had been summoned to the address, he said.
In one incident, Vanderhall complained to cops that his mother was withholding his social services money, Fitzpatrick said.
In another incident, from March, the mom told police Vanderhall had slapped her and otherwise physically harassed her.
She declined to have him arrested. But the next day she went to Family Court and got an order…