A suburban St. Louis man was charged Friday with stabbing four relatives in their home, killing a man and his toddler son and leaving two other people fighting for their lives.

The crime happened Thursday in Maryland Heights, Missouri, a middle-class suburb with a low crime rate. Police identified those killed as Malcom B. Mathis II, 33, and his 22-month-old son, Malcom Mathis III. Mathis' 4-year-old daughter was hospitalized in "very critical" condition, and his 57-year-old aunt was in critical but stable condition.

On Friday, prosecutors charged Traveon Sims, 20, with two counts of first-degree murder, along with armed criminal action and assault. Sims is the nephew of Mathis.

An alleged accomplice, Onyai Turner, 21, was charged with one count of first-degree murder and armed criminal action. Both suspects are jailed without bond and do not yet have listed attorneys.

St. Louis County prosecutor Bob McCulloch said at a news conference that Sims was paroled in May after serving time for robbery. The Mathis family took him in, but later kicked him out of the house. Police Chief Bill Carson said at an earlier news conference that Sims was apparently kicked out six to eight months ago.

"They wouldn't let him stay in the house any longer," McCulloch said. "And I think that is what ultimately led to this."

Mathis' wife, who is also the mother of the children, found the victims in different areas of the two-story home Thursday night. Police believe the older woman and children were stabbed earlier in the day, and Mathis was attacked when he arrived home later.

"The stabbings actually took place over a period of time" from late-afternoon through early-evening Thursday, Carson said.

"This is probably one of the most brutal and violent crime scenes I've ever seen," Carson said.

McCulloch declined to discuss specific details of the crime but said Turner was an "active participant."

Police tracked down the suspects at a St. Louis motel, where they were arrested without incident between 1 a.m. and 2 a.m. Friday, Carson said.