A deranged Brooklyn man who stabbed his stepfather to death this morning then went on a killing spree, butchering his girlfriend and her mother before gravely wounding two others in his wild escape, police sources said.

Early this morning, Maksim Gelman, 23, repeatedly stabbed Alexsandr Kuznetsov, 54, after a heated argument in his Sheepshead Bay home, police said. The body was discovered about 5 a.m.

Gelman fled the scene in a gray 2004 Lexus ES 330.

He then resurfaced around 4 p.m. when he showed up at his girlfriend’s house at 2466 E. 24th St. Gelman allegedly stabbed to death the woman, 21, and her mother, 50, before running outside and carjacking a 1995 Pontiac Bonneville, knifing the driver.

The 60-year-old driver was stabbed three times in the chest and is in stable condition at Lutheran Medical Center, sources said.

He took off the in car and hit an 80-year-old male pedestrian at Avenue T and Ocean Avenue and fled once again.

He remains at large.

Anthony Riggio, superintendent at the building where Gelman lives, said it was “no secret” that Kuznetsov and his stepson didn’t get along.

“One time I asked him, ‘What’s your father’s name,’ and he replied, ‘a–hole.'”

“I never thought that I’d see this, him stabbing him to death,” Riggio added. “I could see them maybe getting into a fistfight.”

He described Kuznetsov as a “hulking guy” and Gelman as “a tall, skinny kid.”