(CNN) Philadelphia police are searching for leads after a violent weekend that left a 2-year-old girl shot to death and an 11-month-old in critical condition with four gunshot wounds.

The 2-year-old girl was killed Sunday afternoon when somebody fired a rifle into a home in Kensington, in northern Philadelphia. She was hit in the back of the head and pronounced dead at the scene, police said.

The girl's mother was holding her at the time and sustained a gunshot wound to her arm and a grazing wound to her head, police said. A man in the home, who police said was there to clean carpets, was shot in the abdomen and is in critical condition. Also inside the house were the slain girl's grandmother and three other small children.

A 2-year-old girl was killed and two adults wounded when someone fired into a house Sunday, police said.

Philadelphia Police Captain Jason Smith told reporters Monday the 7.62 mm rifle rounds found at the house appeared to match rounds fired minutes earlier at a black SUV several blocks away, and were likely fired by the same weapon.

"You should always feel that you are OK in your home, and you should feel that when you're with your parents you're safe." said Acting Philadelphia Police Commissioner Christine Coulter at a Monday press conference. "These scenes should not continue to happen in our city. We're a great city, and we need to do better. We have to do better."

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