CLARISSA Sadowniczak doesn't yet understand the hole some anonymous villain tore through her young life Thursday night.

Friday night, the 2-year-old sat wide-eyed as her family wept around her, their tears catching in the light of a dozen flickering candles.

She glanced at the bouquet of balloons tied to the railing in front of her Port Richmond rowhouse, the one she shared with her parents. She spotted a pink one and reached for it, her tiny hands grasping at its ribbon.

A family member untied it, passed it to her. The little girl released it immediately, shouting "Bye, mommy" as it spiraled up into the night sky.

The tears flowed more freely after that.

"Stephanie never hurt anyone; she was a beautiful person," Laura Sadowniczak said as she surveyed the vigil set up for her son's slain girlfriend.

Pictures of Stephanie Dzikowski, 22, throughout her life stared back at her: A smiling kid, not much older than Clarissa, sitting for a portrait; a young woman grinning next to her friends.

"She had a perfect family; she couldn't have been happier," Sadowniczak said. "Now, someone took that away from her, and my granddaughter will never see her mother again."

Two young relatives of Stephanie Dzikowski join the vigil outside her Port Richmond home. (JOSEPH KACZMAREK/FOR THE DAILY NEWS)

An unidentified man darted into Dzikowski's Port Richmond rowhouse late Thursday, marched up to the second floor and shot her in the head, while Clarissa sat nearby.

Medics pronounced the young mother dead at the scene at 11:06 p.m.

A man in a gray hoodie was spotted by a neighbor running from the scene. Investigators didn't have a motive as of Friday night, but believe the house was specifically targeted: There were no signs of forced entry, and nothing appeared to have been stolen, police said.

The victim's live-in boyfriend, Sean Sadowniczak, was being held by Homicide Unit detectives for questioning Friday night, hours after first being brought in, according to a police source.

Dzikowski's murder floored her neighbors on Aramingo Avenue near Clearfield Street. She had lived on the street for 18 years, and most knew her from when she was a toddler.

"She was a great mother and a great friend," said Marie Larkins, 48. "The big question is, 'Why?' - she didn't have any enemies and everybody around here loved her."

Larkins was startled Thursday when Sean Sadowniczak ran onto her porch and banged on her door.

He was in a primal panic, screaming, "Somebody shot her, somebody killed her," Larkins said. He could barely compose himself long enough to give an address to the dispatcher who had answered his emergency call.

Larkins, along with her niece Elizabeth Sterling, ran a few doors down to Dzikowski's house.

They found the young mother collapsed in her second-floor bedroom, covered in blood.

"I laid Stephanie down on the floor. I was trying to do CPR, but it was too late," Sterling, 25, said, as her eyes filled with tears.

"I tried to do anything I could to save her. For someone to do this in front of her daughter . . . you're a coward. Justice is going to be served."

Dzikowski and Sadowniczak lived with her father, Stephen Dzikowski. The couple was supposed to move into their own house on Aug. 14, one down the block from Sadowniczak's mother, who often watched Clarissa while her parents were at work.

Neighbors said Sean Sadowniczak was at Perri's, a nearby Italian restaurant, when the shooting occurred.

His girlfriend had sent him to pick up some iced tea while she cooked dinner, Larkins said.

Neighbors spent all of Friday watching the memorial to Dzikowski grow with flowers, stuffed animals and candles.

Her father, Stephen, tried to return home. He lasted about five minutes.

"He couldn't stand it," Larkins said. "He can't be here right now."

Dzikowski's Facebook page is filled with photos of her doe-eyed daughter, of the young mother hamming it up for selfies or posing with her boyfriend. Her murder is indescribably heartbreaking - and deeply puzzling.

Friends recited her schedule with ease - off to work as a dental hygienist in the morning, then back at little Clarissa's side at night.

"She didn't have problems with nobody. That's why everyone's confused," said longtime friend Destinee Mulero, 19. "She was always happy, always with that little girl."

The consensus yesterday on Aramingo Avenue was that it was a planned attack by someone who knew the couple - nobody heard their pit bull, Reina, make a sound that night. And the dog normally gives strangers a very vocal warning when they first enter her owners' home.

Nearly 24 hours after that horrific night, about a hundred people crowded in front of Dzikowski's porch, honoring her memory.

The Rev. Dennis Fedak, the pastor of the nearby Our Lady Help of Christians church, led the group in the Lord's Prayer.

"We ask you, our Father, to put an end to the senseless violence that plagues our city," Fedak said later in a brief sermon.

Kathy Sterling, Elizabeth's mother, said she saw Dzikowski a few hours before she was gunned down. "She had just gotten home from work, and I think she was going to pick up her daughter from her grandmother," Sterling said.

"She was very funny, very loving. I'll never forget any of that, because she'll always live in my heart," she said.

Sterling paused, and took a deep breath.

"She was just living her life. She had a career, and some punk took it away from her."