Two young children and a pregnant mother were sent to hospital suffering knife wounds Saturday morning after a grisly attack in Burlington, Ont.

A 29-year-old woman, identified only as Yelda, plus her seven-year-old son Omar and five-year-old daughter Lina were rushed to hospital around 1:30 a.m.

The mother and daughter were reportedly in serious condition while the little boy was in critical condition. All were suffering stab wounds and gashes.

Tracy Lockhart heard the mother's cries for help.

"She was like, 'help me, help me, no, I'm not okay' and she was just freaking so I went (and) called 911 right away," Lockhart said.

Halton Regional Police responded to the scene after receiving calls about the incident at a townhouse complex on Guelph Line north of the QEW.

Officers arrested a 24-year-old woman at gunpoint. Neighbours told CTV's Jim Junkin that the suspect is the victim's sister-in-law.

Police are trying to piece together a motive for the attack.

"We don't know yet," Staff Sgt. Dan Gheller said.

"The investigators are still doing interviews. At this point I don't have that information."

The mother underwent surgery and her unborn baby is not in danger. The conditions of the two injured children have stabilized.

With a report from CTV's Jim Junkin