DETROIT -- A woman and four children were tied up and beaten to death in this city, which already had been shaken by a surge of killings this year.

A 13-year-old girl alerted authorities after escaping from the house where a 33-year-old woman, a 16-year-old boy and three girls, ages 9 to 14, were found dead Thursday.

Investigators were interviewing a suspect Thursday evening but he had not been charged.

Police gave no motive for the slayings and released no other information on the victims or the suspect, but relatives said he was the father of one of the victims.

Deputy Chief Cara Best said police found the weapon they believe was used, but she would not say what it was.

Family members and friends of the five killed trickled to the gray bungalow throughout the morning and early afternoon, weeping as they learned of their loved ones' deaths. Paramedics were summoned to treat at least two women who collapsed.

One young man ran across the field yelling, "Where's my sister? Where's my sister?" After talking briefly to a group of people near the police tape around the scene, he threw himself on the wet grass and sobbed.

Officers draped a white sheet across the porch of the house and loaded the bodies from the house to a van.

William Parker Sr., who showed up at the scene, said three of the children killed were his: William, Wanee and Wrandell Parker. He said the other child was the suspect's daughter.

Tyann Shelton said the 33-year-old victim was her sister, Lisa Shelton.

Police said they did not know when the killings occurred.

Nancy Marrugi, who lives across the street, said she didn't know the victims, but that the woman had lived there with her children for about six months.

"The kids used to play all the time, play with their dog," a gray-and-white pit bull, Marrugi said. "They seemed very happy."

The neighborhood is a mix of neatly kept houses, abandoned buildings and homes under construction.

"They're trying to build up this neighborhood, clean it up, you know," said Felicia Johnson, 25, who works nearby and stopped when she saw the police cars.

The killings came amid a wave of violence that has swept the city since the beginning of the year. Detroit saw its lowest homicide total since 1967 last year, but is on a significantly bloodier pace this year, with 102 killings so far.

On Feb. 16, two police officers were gunned down during a traffic stop. On Sunday, a toddler was accidentally killed when a woman taking care of her handled a shotgun carelessly, police said. The woman was charged with involuntary manslaughter.